Unless your state has really weird tax laws, contributing to an IRA reduces the amount of income that you get taxed on.

So if you make $100K and you contribute $10K to a traditional IRA, then for income tax purposes, you made $90K. (You still have to pay Social Security + Medicare on all $100K.)

This should be the same way for federal and state, though it's possible you live in a state with weird rules and would need to check the rules specifically for your state to make 100% sure that's the case. (I would be stunned if it isn't, though.)