So this has bothered me for 3 years! I found an app that calculates it. It’s not perfect, ie. you have to manually look up the order and it wont work from my phone yet, but it does this exact thing. Saves me an hour out of my day. They also just updated their video on what the app does using my store which is pretty cool. They asked after my review of their app. Anyway. I like it. I hope they continue to make it better. It would be helpful if it worked with gorgias.