Okay, this is interesting -- one etiquette page I just read says to tip on the total before tax, not the final tally! That's news to me. I usually tip 20% on the whole thing. Huh. So, guys -- which way have you been talking about? Pre- tax, or final count?
I just look at the big number at the bottom of the bill, which includes tax.
I honestly don't put that much thought into it, though.