An Old Riddle

Three good friends frequent their favorite restaurant and get a check that comes to a total of $2.50. Each man hands the waiter a dollar bill. On his way back with their change of 50 cents, the enterprising waiter decides that it would be needlessly difficult for the three patrons to divide up the 50 cents, so he pockets 20 cents and hands each man a dime. Now, each man paid a dollar and received back 10 cents in change. So each man really paid 90 cents. From all three, the total was $2.70. The waiter of course has 20 cents in his pocket for a total of $2.90. The riddle is that since they started with $3.00 but we have accounted only for $2.90, where is the missing dime?

I will publish the answer tomorrow at 6pm.