Brainteaser #40- Missing Dollar -

Tom, Dick, and Harry are attending a conference together out of town and are staying overnight at a nearby hotel. The hotel has a special for conference attendees and the clerk charges them $30 for the room. Each takes out a $10 bill and pays the clerk. The men then go to their room. When the manager returns to the front desk, she realizes the clerk has overcharged the three guests, the special rate is $25. The manager asks the clerk to return $5 to the guests.

As the clerk walks to the room, he realizes that he can't evenly split $5 among three people, so he decides to give each of the three guests $1 each and illegally pocket the remaining $2. When the clerk arrives at the guests' room, he tells them that they have been overcharged by $3 and he hands them each $1.

So, Tom, Dick, and Harry have each paid $9 for a total of $27 and the clerk has $2 in his pocket. That makes $29. However, the guests intially paid $30. Where's the "missing" dollar?