My last cruise, I thought I would be remembered by the crew for giving out $2 bills as tips. So I got $100 worth from the bank.
Let me tell you, the crew remembered, and it wasn't for a good reason. No one wanted the bills. I would get asked if I had anything else. They can't spend them. No one thinks they are real. I think many of the crew accepted them wondering if I as being a jerk handing out fake money.
When I tried to buy one of those casino chip souvenirs in the casino, the cage wouldn't even take them.