Thanks Jason, Dani updated this and I was able to easily apply this to my cart.
It works beautifully and I'm very pleased with the results. With this technique, I'll be able to apply it to other things that I didn't realize I could do.
However, I don't understand the concept behind the using "Calculations" vs using "discounts/charges."
Can you tell me, as a general rule, when Calculations should be used vs Charges/discounts?