A shirt at shop #1 is $19.99, and shop #2 sells it for $20. They're essentially the same, so why do we go for the one that's one cent less? Because we tend to remember the first numbers rather than the last, so 19 seems like a better deal than 20. If it only takes one cent for customers to pick shop #1 over shop #2, retailers will keep doing it.
Prices That Ends in .99 or .95