Old school but all the machines for paying in cash in Japan are so optimized for speed. Train stations, onboard buses, convenience stores. Just throw in a handful of coins and it quickly picks what it needs and returns what it doesn’t.
In other countries (eg australia), the ticket machines could only take a single coin at a time and would reject if you did it too fast.
I believe this is one (of several) reasons why cash has continued to be dominant in Japan.
Boston was the last major city I saw to actually add this in the US (every other major city metro I've seen has it). Boston got it last Spring or Summer if I recall. The MBTA is a nightmare, but at least I don't have to reload my Charlie Card anymore...
The best part is it's very useful for getting rid of lots of smaller denomination coins, just dump them all in and the machine will give you the fewest number of coins back that equal the balance.
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.
In other countries (eg australia), the ticket machines could only take a single coin at a time and would reject if you did it too fast.
I believe this is one (of several) reasons why cash has continued to be dominant in Japan.