If you choose the sales tax deduction, there are two methods you can use. One is to list all your sales tax from your own records. This method does not have the "major purchase" addition, you simply add it in with all your other sales tax.
The other method is the optional IRS method, where the IRS estimates your sales tax deduction based on your income and other facts. When using this method, you will be asked about extra sales tax on major purchases.
