Normally you don't owe sales tax on inventory you purchase for resale.
QB doesn't track sales tax on purchases. If you need to track it, perhaps in order to get refunded for it when you file your sales tax forms, then you can add it as it's own line item on the bill. Probably, there's no reason to enter multiple line items for the tax.
If you don't intend to get a refund for the tax paid, then the tax is an expense to you, part of COGS. In this case include it in the item's price paid.