Think of it like $20 bills, $10 bills, $1 bills.

If you’re buying something that’s $9, use a $10 bill.

One difference, however, is that in fiat world, you get charged based on the dollar value, whereas in Bitcoin world, you get charged based on the vByte file size. So you want to use the minimum number of “bills” or UTXOs that will cover the transaction, regardless of the dollar amount, to minimize fees.