I have seen several documentaries(not the best source, I know) and read a few things which claim or suggest that the Nazis either practiced or were at least interested in occultism. I know that a lot of Nazi idealology centered around German superiority and German and that German myths and legends were corrupted into being more Nazi-friendly. I also know that the Nazis collected plunder from all over Europe when they invaded.
However, these are far from claims that Nazis, specifically Himmler and the SS, practiced the occult. How true are said claims? My gut tells me that these are likely either greatly exaggerated or completely false, because the idea that the Nazis were occultists (or as many would say "Devil Worshippers") is fun to believe. But, as I said, the idea is fun to believe and I would like it if there were at least some of it were true.
Accurate for Himmler but largely overblown and not widespread when it did exist. I'll outline three popular points on the connections between Nazism and the occult, and finish with some source links. Almost everything here can be found in the wiki article Religious views of Adolf Hitler but also in associated wikipedia articles. The key principle of any Nazi party actions is how everything they did was to support a strong ethnic state, and every institution was bent to serve that purpose.
The first thing I want to point out is why the Nazis would have given the time of day to anyone espousing occult beliefs. Nazi ideology was that ethnic Germans were the descendants of an Indian race called the Aryans, who in the past had left north out of India and conquered large swaths of territory (possibly all of Europe though I could find this claim made in explicit detail) with the strongest Aryans settling in Germany. Thus, while Germany was majority Christian, at least nominally, this was considered by Nazi leaders a deficit of the race. For example, Hitler called Christianity a "religion for slaves". Thus for some Nazis neo-pagan and occultic beliefs were seen as ways to go back to the pre-christian glory of the germanic people. Although as a matter of pragmatism Hitler also considered this occultism "nonsense". But for both religions Nazi ideologists created their own versions of it that bent their entire meaning towards the supremacy of the german people and their state. The neo-pagan movement that came out of this is called Wotanism, which still exists today among neo-nazis, though it is my understanding there are some neo-pagans that worship Wotan that are not related to neo-nazi groups either. You can even find discussions about this on reddit if you're interested, but that is quite a digression from the question for now. I'll talk about the new Christianity invented for this, Positive Christianity, and both of these are discussed a bit more in the third claim below.
A second point is that is often suggested that the Nazi use of the Swastika came from tracts published by the Theosophic Society, an international occult organization that was popular from the late 1800's until the 1950's (it technically exists today, but is virtually defunct). Not that the Theosophic society endorsed Nazism but Theosophy was the most popular form of esotericism in Germany and Austria in the first half of the 20th century and any cosmopolitan (i.e. the higher up) officials in the nazi party would have been familiar with it. This may have been the introduction of the popularity of the Swastika for the Nazis although it's origins in Indian culture were well known to them, indeed the reason they adopted its use, in order to associate themselves with the Aryan race as discussed in the previous paragraph.
A third point is that occultism (worship of ancient germanic or norse gods) were influential to Nazism. This is not particularly true, Hitler called occultism "nonsense", but some of Hitler's inner circle, in particular Himmler but also Rudolf Hess and Alfred Rosenberg held these beliefs. On the other hand, Hitler saw Christianity as "indelibly Jewish in origin and character" and a "prototype of Bolshevism", which "violated the law of natural selection". As stated earlier Hitler personally and Nazi ideology in general was amoral and aimed to shape any institution including religion as much around Nazi ideology as possible. Hitler suppressed both Catholic and Protestant churches and replaced them with a state church (called the German Church) that taught a Nazi designed religion called "Positive Christianity". "Positive Christianity" posited that Jesus was an Aryan fighting the Jews, that the Bible had been edited by Paul (the Apostle) to hide this fact, and that Jesus' original message was one of combat and loyalty to one's race. Hitler made The German Church the only legally sanctioned church in 1937 as he considered christianity proper to be a weakness, and a blight to the german state. He put neo-Pagan Alfred Rosenberg in as official Nazi ideologist. Just to be clear he has no intention of replacing Christianity with occultism though, his state church was largely considered a temporary transitional measure until religion could be extinguished altogether.
That's about it for the extent of occultism in the Nazi regime proper. Neo-Nazis also largely follow either atheism, Positive Christianity-style churches or Neo-Pagan occultism.
Edit: If you're interested in learning a bit on Neo-Nazis in America, Louis Theroux did a documentary on survivalists, and the last part of it is on Neo-Nazi survivalists, and they visit a Positive Christianity based "church". link (note, it's a little creepy)
Edit 2: Ok I'll be a good redditor and link some wiki articles (non-exhaustive list):
Edit 3: there is a wiki article called "Nazism and Occultism" but the article is more about answer the question "Where did myths about Occultic practices in Nazism come from?" (You'll see what I mean if you look at the table of contents.) I still prefer the prior list of articles here to answer OPs question.
There's a small section in the FAQ regarding this. You can find it here. Hopefully they help :)