> I've witness several cashiers getting their phone out to calculate basic change. Don't point-of-sale devices do that already? The cashier inputs the total yo

> I've witness several cashiers getting their phone out to calculate basic change. Don't point-of-sale devices do that already? The cashier inputs the total you gave them, and the point-of-sale device shows the exact change on its screen (and releases the cash drawer lock). It might seem useless, but it reduces the risk of an incorrect mental calculation (like R$ 100 - R$ 77 => R$ 33 instead of R$ 23). Some even display which coins and notes, and how many of each, the cashier should get for the change.