This hurts my brain!

so three gys walk into a resteraunt to get some food, their total rings up to $30. the manager says it is only suppost to be $25, and is ordered to give five back to the three men, she grabs 5 1 dollar bills our from the cash register, and she notices, that it cant be split evenly, so she gives each man back $1, and keeps a $2 tip. here is where it gets tricky. because each man was given back $1 they each paid $9, wich rings up to $27, and the waiter has the 2 dollar tip, which goes to $29,

where did the extra dollar go?