Cool tees is having a back-to-school sale where all t-shirts are discounted by 15%. joshua wants to buy five shirts: one cost $9.99, two cost $11.99 each and two other cost $21.00 each. what is the total cost of the shirts including the discount. by law, sales tax is calculated on the discounted price of the shirts. would the total cost of the shirts including the 6.5% sales tax be greater if the tax was applied before a 15% discount is taken, rather than after a 15% discount is taken? explain.