Your question confuses at least two topics.
1. You can’t pay your state taxes from your federal refund.
2. You can’t use state sales tax to offset your federal income tax bill.
3. What you can do is used state tax as an itemized tax deduction on schedule A of your federal return. If your total itemized deductions are larger than your standard deduction, that will reduce your taxable income and you will pay less tax overall, but it is not a direct dollar for dollar credit.
When calculating what amount of state tax to deduct on your federal return, you can either use state income tax that you paid or state sales tax that you paid. When using the sales tax deduction, you can either use actual tax that you paid from your receipts, or you can use a Standard estimate that the IRS calculates based on your income and local tax rate. When using the standard IRS amount of sales tax, you can increase that by the amount of sales tax you paid for the purchase of a vehicle.
When you prepare your tax return in TurboTax, simply go through the program and list all of your deductions. TurboTax will tell you whether it is better to use the standard deduction, the state income tax deduction, or the state sales tax deduction.
