I have a 401k through my employer. Can I also open an IRA and take tax deductions for both?

Maybe if your income is in the correct range ... if you enter the contribution amount you want to make into the program it will tell you how much is deductible and how much isn't then you can make an informed choice. 

Your 401(k) is already deducted by your employer in your W-2 - that is the only place that it is reported.