Interesting question where is one cent lost?

I am submitting here one riddle, hope you have the logic for this.

Three guys went to a cafe, and each of them took a drink of worth 10 cents. After the drink, every one took out 10 cents and paid the bill of total 30 cents went left the cafe. After a while, the cafe manager realized he should provide them discount of 5 cents so he asked his assistant to back then 5 cents. Now the assistant got confused, how to give 5 cent to three persons. So he took 2 cents by himself and returned one cent each to the three guys.

Now look, each of the guys paid the sum equal to 9 cents, so the total becomes 27 cents, and the two cents is taken by the assistant. So the total is 27+2=29 cents. Then where is the one cent gone?