Hmm, I argue that it's impossible, even in principle, to have a correct calculation of state sales tax due.
The Court noted a specific case listed in the story -- the tax depends on the purpose that yarn will be used for. The same is true for some food taxes, where there are different rates depending on how it will be consumed. Is it a taxable snack, with a junk food excise tax, or part of a healthy meal? Is it a flavored extract for cooking, or a liquor for cocktails?