Honestly...

You don't tip in Japan. Despite this, I wouldn't be surprised if it's the best service in the world. I've heard a few stories of foreigners who leave a tip on the restaurant table and the owner comes running down the street to give it back to them. 

This story takes the cake though.

At the weekend, we went to the supermarket and picked up a few things. One of them was a small pizza that cost around 200 yen. We got a call today from the supermarket telling us that they'd overcharged us by 30 yen. 30 yen is about 20 pence or 30 cents. They apologized profusely and wanted to come to our apartment to give us the money. Of course, we told them not to bother but they insisted on putting it aside at the shop and told us to give our name and pick it up the next time we're there.