However, as a one-time cashier, I am at odds with them. Cashiers at grocery stores are basically automatons. In many cases, if there is no bar present and there is a long line of customers, it is almost a sure thing the cashier will keep checking food in on the first person's bill. This can be more than a niggling inconvenience. If an expensive item or several items cross that grape divide, the cashier can't necessarily cancel the transactions.
Cancellations exceeding a certain monetary amount have to be keyed in by a supervisor.
On a very busy day, that can take several minutes, making customers antsy and irritable. Yes, there is such a thing as grocery rage. So please, if it's a busy day, either leave an appreciable gap between your order and the next, or use the foo'bar. You'll be doing the cashier, and possibly a few dozen other customers, a courtesy. A week ago today, my neck went to war against me.