You can deduct a portion of the TurboTax product, since it is a necessary and ordinary business expense. However, you can't deduct the full cost of the product, since you use it to prepare your personal taxes also. So, multiply the cost by a factor based on how much time you spend on the rental entries in TurboTax divided by the total time necessary to prepare your tax return.
You enter it as an Other Expense in the rental section of TurboTax.