Though usually I would also let something like this slide, I happen to agree with Nostrildamus. I probably wouldn't have done the penny tip, since that's reserved for when they spit in my food, but I might have given her 10% instead of my usual 20. She doesn't get to make any decisions, like some people have pointed out, so it's not -exactly- her fault, but she should have handled it better. She should have just apologized and asked if they wanted to see the manager. Canada might be a gray area, since apparently they use US and Imperial pints, but still, it's the principle of the thing. If either the waitress or the bartender (who really ought to know better) said "We're really sorry, we don't have bigger glasses to serve you in and we can't come down on the price or our manager will strangle us, but we'll change the board", I would have been fine with that. But they didn't do that, they argued with the guy. I feel like that shouldn't happen in a restaurant.