When we are talking with each other about the cost of something, the conversation is between just the two of us, I say "That is $15 dollars," or "That is $30,000," or "That is $200,000", and the salesperson interupts and says, "No, $14.99," or "$29,995," or "$199,900."
I used to try to explain that I was just making it easier for me to think about something, estimate additional costs, and the percentage is almost insignificant, but finally gave up. Be it a shirt, a car, or a house, the sales person seems to think that a penny, 5 bucks, or $100 dollars is going to make a difference on how we think and decide on a purchase.
Now, we've just given up and say not to worry about it, we are thinking out loud.