Just a reminder: always double check your receipt before you leave the store. I do this anymore out of habit and in the last 2 weeks it has saved me around $3. That is not much, but for a little bit of time at the service desk it is worth it to me.
I don't know about you, but it bugs me immensely when I am overcharged for something, even if it is only a couple of pennies. Probably silly, I know and I have learned not to sweat a couple of cents but it still bothers me just a bit.