While I have no doubt there were isolated incidents, you often hear of uncontested armies in "enemy" territory doing horrific war crimes. Moreso the concept of war crimes in the 1800s wasn't what it is now.
More can certainly be said, but this answer by /u/Johndeville gets at the essentials of what you're asking. In short: though Sherman's campaign late in the war is well-remembered for bringing relentless "total war" to the region and causing a great deal of economic and infrastructural damage, you will encounter basically no evidence of widespread "atrocities" like murdering civilians or surrendering soldiers, torture, rape, and so on.