B-tier power: Exact Change. Any time I want to pay for something with cash, I have the power to reach into my pocket and pull out exactly the amount of cash money needed to do so. This has no effect on anyone's money anywhere else, like wallets or bank accounts - it just magically appears.
Infinite petty cash. you can't buy most big-ticket items with cash, like a new car or a house, and you can't spend it online, only in person. And, since you can only do it to pay for things, you can't just pull money out of your pocket forever to hoard. You might be able to trick it with the right accomplice, or just use it to buy gold and then resell it, but it's pretty inefficient.
While I take your point you very much can buy a new car with cash.
It would be inefficient to game the system but it could be gamed. It would feel like petty larceny but I'd start with several maxed out Visa gift cards so I could make online purchases. Maybe money orders if that's still a thing.
Edit to your power: You still need dollar amounts, and if you don't have, then you don't have any change.
Eg. Cost: $4.52, and you have $5 in your pocket: you pull out $5.52, or if you have $4 in your pocket, you pull out $4.52. If you have $3 in your pocket, you pull out $3.