My employer paid for all of my tuition expenses. I inputted the amounts on the 1098-T form I received from the university. Why am I receiving a tuition deduction?

Box 5 of the 1098-T does not usually included employer payments.  Later in the interview you will be asked to enter employer reimbursement.  Enter only the tax free* portion (the first $5250 is usually tax free). 

*The "Learn More" link says "If a student paid for these expenses and was reimbursed by an employer, enter that reimbursement amount not already listed on a 1098-T, W-2 or other tax form.

Alternatively, if you know you are not eligible for a Tuition credit or deduction, you can just not enter the 1098-T.  The 1098-T is only an informational document. The numbers on it are not required to be entered onto your tax return. However receipt of a 1098-T frequently means you are either eligible for a tuition credit or deduction or possibly your student has taxable scholarship income. You claim the tuition credit, or report scholarship income, based on your own financial records, not the 1098-T. 

If you claim the tuition credit, you do need to report that you got one or that you qualify for an exception (the TurboTax interview will handle this)