Having owned a store for 26 years, I would have apologized for my mistake and made it right, and then maybe offered a coupon for your next visit. Customer service and word of mouth are so important in a small business. And even if he is the owners, son, you should nicely let the owner know. It always shocked me how many young people would come in our store and couldn't count change, and I think he was embarrassed and became defensive. If he did this to you, there are probably other customers that he has mistreated.