Nobody wants to deal with coins
This “industry secret” isn’t really a secret at all. Nobody, and we mean nobody, likes dealing with coins. If you pay $10 for a $5.46 bill, getting the $4.54 in chance is a hassle for both the cashier and your wallet. So, if you’re getting gas, try and make round it off to the nearest dollar.
This is especially true if you overshoot while paying with a prepaid card or note. But if you can’t avoid the convenience of paying an even $1 or $5 over the prepaid card, don’t stress out. Sure, the cashier will be inconvenienced to count the coins, but he or she will get over it.