There are a bunch of other threads that have a discussion on it, but I will post here as well.
It is very simple to pay taxes on cryptocurrency in the United States. It is treated as property in the IRS's mind. So you would handle it the same way you would handle gold or silver profit/loss. No further discussion necessary unless they change the law.
But what about for shapeshifts and stuff? It's almost like a barter, one good for another good.