Get your taxes done using TurboTax

You pay tax on your total income for the year no matter how many jobs you have.  Each job is holding out the amount for that one job like it's the only job you have.   But when you have more than one job (W2)  the total income for all all might put you into a higher tax bracket.  So you may end up short for the year.  Claiming Single and 0 should work out ok.