Jews and tipping

I went to lunch with a jewish friend of mine and he paid $15 in cash and got $3 in change instead of $3.20 because the waitress didn’t feel like getting a bunch of coins out. He sat there looking at it shocked and pointed to it a bit, but I had no idea what he was going on about because I hella don’t give a shit. After we left the restaurant he complained for half an hour about how the waitress didn’t give him his twenty cents and he was legitimately shocked and angry about it. He ended up tipping $2 after we complained to him a bunch.

How did the holocaust only happen once?