Today a rare event happened but I'd like to prevent it from happening in the future.
I offer free shipping for orders $100 and over. I received an order for $94 which should have had a $6 shipping charge but it didn't. The reason why is because the sales tax was $6.23 putting the order over $100 and the customer received free shipping.
I let it go because I don't like to appear petty but I'd like to know if there's a way to leave out sales tax when calculating shipping.

Thanks
Carol