If I put $5,500 into an IRA today, will that lower my taxes by $5,500?
No. It doesn't work that way.
If you contribute $5,500 to a Traditional IRA, you can deduct up to $5,500 from your taxable income—not your tax bill. It's a tax deduction, not a dollar-for-dollar tax credit.
So, if you open a Traditional IRA for $5,500 (or contribute $5,500 to an existing account), it would reduce the amount of income you get taxed on by up to $5,500. In the 15% tax bracket, that translates to $825 off your tax bill.
And if you put $5,500 into a Roth IRA, you won't get any deduction at all.