Ok then, if that is the case the question becomes, how close could someone duplicate a government issued bill and NOT get in trouble if the bill had the words "NOT LEGAL TENDER" on it?
I suppose the court's test would be whether a normal person would be likely to confuse it with real money---by some standard for the terms "normal" and "likely".
Additionally, I guess a court might look at your intent for printing that bill. If you actually try to spend it, you're on the hook. But if Andy Warhol printed a series of "dollar bills" just to exhibit them in a gallery, that would probably be a different case.
I am not a layer, and these are just my idle speculations.