Do not add the $5250 to box 5 of the 1098-T. Later you'll be asked about other scholarships and assistance. You'll be given a specific box for employer assistance/reimbursement. Enter there, but only the tax free portion ($5250 in your case).
Note: if your employer paid the school directly, some (but not most) schools may have already included that amount in box 5 of the 1098-T. If so, don't duplicate the entry at employer assistance..
