I've never seen a reference to currencies used - but like everyone, I haven't read everything. In the archaeology, we did find poker chips. They weren't really common, but we did find them on occasion. Unfortunately there was no $1 (or anything else) stamped on them, so we couldn't tell what the chips were worth.

Archaeologically, pennies were rare in Virginia City, Nevada (my office excavated four saloons and numerous other sites between 1991-2012) - and this is in keeping with the written record, which emphasizes short bits (a dime), long bits (the balance paid with a quarter when you get a dime back in change) two bits (a quarter) etc. We did find nickels, which tells us something about non-saloon exchanges, namely that things were being purchased in denominations of five cents or more.

In modern casinos, games range in a full spectrum of denominations - everything from penny slots to poker and other games exchanging thousands of dollars - and I expect one would find that as well, but I have no evidence for that. It simply makes sense and it fits human nature: some people are wealthy and feel a thrill when risking high stakes; some people are poor and feel the need to risk everything - which in their case isn't much!

Oral tradition tells of a faro table where people lost as much as $10k and a single play - Virginia City's Delta Saloon exhibits the famed "Suicide Table," a faro table made famous because it had been the location of so many of these high stakes losses that several people had committed suicide there. It is important to emphasize the words "MADE FAMOUS" - there is no evidence that this story is true, and it was possibly made up in the 1930s or 1940s to cater to the emerging tourism trade. On the other hand, sometimes these things are true: just because something is folklore doesn't mean that it is false!

There is also a story (emphasizing, again, that folklore may be present!) of Silver Baron John William Mackay (1831-1902) playing poker at the so-called "Millionaire's Club" - known with the formal name, "The Washoe Club," which was a members-only rich men's retreat. The story describes thousands of dollars at stake and Mackay pushing away from the table saying he had once enjoyed poker because it was thrilling when he was wagering money that would be painful to lose and when he might enjoy the thrill of making a big haul, but since he was worth millions (he was one of the richest people in the US), he felt none of the excitement and the game had been ruined for him.

That story is also likely apocryphal, but it is easy to imagine poker games in the Washoe Club reaching those proportions. Unfortunately, the key word here, again, is "imagine."