The bartender presented me with a bill which included both the dinner and the beers. I tipped 20% on the entire bill and gave the total to the bartender. I guess that makes sense since the bartender was the one who took my order for the dinner as well as the beers and also placed the plate of food in front of me (although one of the waiters had to run the food up two flights of stairs to the bar). I guess it's up to the bartender to "tip out" the waiter. No other practical way of handling the tipping that I can see.