In my experience with the US the strategy is to minimize cashiers, ideally have one person running a full service lane and managing the self checkouts between their customer line. Oh and they can handle returns and exchanges too. And online order pickup. Oh and also "frontline" customer complaints. $10 an hour should cover this.

The stocking crew is separate and it's a 50/50 chance if they're trained on registers.

Edit: this obviously depends on the store and staff size, but this seems to be the procedure for most big box retailers.