Does it bother you when you don't get all of your change back?

Scenario: You're eating out and the time has come to pay your bill. Your total is $13.78, so you give the waitress a $20 bill. She gives you $6 back but not the remaining $0.22.

As a server, I do this all the time if I don't have the correct amount of change on me. Sometimes, finding change seems like much more of a hassle than it's actually worth. I never thought it was a big deal until one of my customers went out of her way to thank me for giving her all of her change. According to her, a lot of people are bothered when they don't get correct change back but don't like to make a big deal out of it. Is it a problem that she assumed it was okay to keep the change?