If you are entering sales tax paid, you have a choice to enter the totals from your receipts or to let TurboTax calculate an amount based on your sales tax rate and your income.
Sales tax is an itemized deduction. If your state has a state income tax, you have to choose between using the deduction for your state tax paid OR the sales tax deduction, whichever is higher. The TT process will suggest one or the other as you prepare your return.
https://ttlc.intuit.com/questions/1901222-which-deduction-should-i-choose-sales-tax-or-income-tax
https://ttlc.intuit.com/questions/2566624-how-much-sales-tax-did-i-pay-last-year
In your other post, you said you have no income. And do you live in the USA?
Thats right. I will be resident alien 20 Jan. And haven't any income in or outside US all year.
But taxes are based on 12/31/2017. You have no 2017 income against which to deduct 2017 sales tax.
Did not see the other post. SweetieJean is correct. If you had no income for 2017, there is no point to entering sales tax on a tax return.