If Wal-Mart is so concerned about "family values" and music quality (as evidenced by their stupendous treatment of their employees and their censorship of artists they carry), why are they adverting HP6 on GJ for $16.66?
When I worked in fast food, I had people who would refuse to pay if it totaled $6.66. Or they'd pay extra and refuse the change. We had to go through every so often, into the registers, and reprogram them so that you couldn't add up that amount. Just keep track of the orders that total to that, then set it to boot them up to $6.67.