I have spent some time working retail. As a cashier I perfected a routine which I would time how long it would take the terminal, or cash register, to bring up the total. In the eighties it would take a couple of seconds, so I would draw up my index fingers, say your total is, and shoot the register as the total would come up. When there were kids with the parents, they would be most entertained. Make the kids happy and the parents are most likely to come back.
Something else I would do, which I view as a dying art nowadays, is I would coount the change back to the customer, say "Have a super day and thank you for shopping --------." I have worked for Montgomery Ward, Sears, Fretter, K-Mart, and Wal-Mart, not to mention a very short time at a car dealership. Okay, I won't mention it.
I say that it's a dying art because some retail establishments don't practice some basic rules of common courtesy now.
I plan on doing this in reverse. When I go to places like the evil big box store lately, when I get my receipt, I have started to say, "Have a super day and thank you for working at Wal-Mart." That makes their day and maybe we will start hearing this from the cashiers. It would do me some good if I thought they were glad to see both me and my money.