Click on the green flag to delete everything. Click on total after you add the products you want. Click on tax for taxes (Texas' tax percent is 8.25%, so I used this in the calculating). Click on total before you click on tax. Click on delete to delete an item on the list (enter the number on the list, not the product). If you type all, it would delete all. If you type last, it deletes the last item on the list.
This was the final project for scratch in my school. I did it on the day it was issued.