Still not adding up to me. The tip amounts on $8.00 should have been $1.20, $1.60 and $2.00 respectively. Each of these is lower than its counterpart on the bill he described. If the taxable amount was less than $8.00 the suggested tips should have been even lower than that. Perhaps they swung the other direction and doubled the sales tax, then added that amount in before calculating the tip. Wouldn't take too much of a coding bug for that to happen. Would be dumbass code but I've seen some dumbass code in my time. Written a few lines of it I'm sure.