I got a riddle I can't SOLVE!?

You and 2 friends rent a hotel room it's 30 so you split it evenly 10 each. You get 5 back because you paid to much. You each get 1 dollar back so you paid 9 dollars each and 2 dollars for tip. Then you paid 27 because 9 x 3 is 27 then 2 dollars which is 29 wheres the other dollar??