We have the tech in the USA but it’s only ever used for coin counting machines (which themselves are relatively rare).

Not only in coin counting machines.

I've seen people on YouTube using the U-Scan at Walmart like a CoinStar. Apparently if you lift where the coin slot is you can dump in coins and it will process it all. If the total is more than your bill, it gives you the money back.

While I'm not sure about the refund of an overpayment, there are also the toll booths that have buckets to throw change into. Though most tolls seem to be electronic these days.