I feel very sorry for cashiers. I think that might be the most stressful job on the earth. No it's not having to deal with grumpy costumers, although that has to suck, and it isn't the crappy boss always breathing down your neck - making you account for every cent whether losing it was your fault or the employee before you - and it isn't all those stupid produce numbers you are expected to memorize. Those, although crappy, parts of the job are just that; part of the job. No the reason that I feel sorry for cashiers is the illusion they must suffer that the line will never end.
Think about it: you look up and there is three people in line. You finish bagging the costumers groceries and give them their receipt. While looking at the next costumer - giving a warm smile as every good cashier does - you eye catches a costumer falling into your line. The void of the previous costumer has been filled.
therefor, it is never ending, and on a good day the line will stay at three with the rare spike of five or six. But this time of year a good day is five or six and you know that their will be at least one costumer that is especially stressed out and has her three kids all under 4 - themselves stressed, feeding off of there mother.