If you have more than a job then each office puts you as a single they will withheld a standard rate to cover you.
If you have another and another then it hit tax bracket over than your withheld and you will end up paying from your pocket.

Suggestion: Any body doing two or more job each tax filing software will help to determine how much money you have to withheld to match to your income according to filing status. You can ask h&r to withheld more to match your total income.

If your office ask you to fill in w-4 form  , put 0 not 1 for single, that will withheld more fed but for state you can ask then  to withheld extra bucks.

If turbo tax says that then try TAXACT or H@Rblock and find out you did fill in wrong or that was the real result. Check your self.

Congratulations !

For what ?     Good earning!