When giving a customer their change, first place the coins in their hand, then the bills and receipt over them. This way, the coins will not slide off the bills, fall on the floor, annoy the customer, and hold up your line while the customer picks up the coins.
And it's not just stuff like that. If you're on OR nurse, for example, this tip on removing rings from patients' fingers might be useful. I do hope, however, that commanding officers in the United States Navy don't find it necessary to turn to this site for tips on steering a warship. That would make me slightly nervous: "OK, we gotta change course, fellas -- let me Google how to do that, just a minute...hmmmmm...hey, did you know that your armspan is roughly equal to your height? That'll come in useful! Now let's see...steering a warship, ah here we go...Right full rudder!"
(By the way, I'd amend the cashier advice as follows: Don't put the customer's original money into the till until the transaction is complete and they are gone. This will deter the "But I gave you a twenty!" thing when they actually gave you a ten.)