No doubt, you have experienced the following scenario: You go out for drinks and dinner with a group of friends or people you know from work. The beverages flow, time passes and eventually the waiter comes bearing an impossibly complicated bill. It seems like you spend the next hour poring over columns of figures scrawled on a napkin, or possibly the screen of your smartphone, to figure out exactly how much each person owes. By the time you get to the tip, your head is spinning. When the moment has arrived to leave, you hope against hope that your server did not get short-changed in the process.