Salesman giving a discount

Some salesmen don't accept small change when we make a purchase. Example, I purchased a water bottle for 11 AED and I had 10 AED with me. I gave it to him and said that I will give the 1 AED later. He said ok and the next time when I gave him he said, "Its ok leave it". He is not the owner of the shop. He told me that since its a large industry, 1 AED doesn't matter.

In the college library there is a rule that if a person failed to return a book within a certain time limit, he had to pay a fine of 1 Rupee per day till the book was returned. I returned the book 2 days late and told them that I am late. They told me not to repeat it next time. They did not take the 2 Rupees from me. It was a librarian and not the owner of the college or library who told me that.