What is the reason/meaning for cashiers to use ちょうど when accepting money?
This I understand, since 500 Yen are a "round" amount. "Exactly 500 Yen."
If I'm supposed to pay exactly 812 Yen, I understand this, too. "Exactly 812 Yen, [as required]."
What I don't understand is the usage when it's neither the amount required nor a round number. Say I'm asked to pay 612 Yen and I'm giving 1,112 Yen to get a 500 Yen coin in return. The cashier will still often say
Is it just the habit of saying ちょうどいただきます, or is there a different meaning behind this ちょうど than "exactly"?