Tax exemptions Blank Title 119970

Epicor 9.05.701. I have varied requirements for collecting sales tax and am struggling with the set up to allow for the auto calculation of taxes at invoicing. The requirements are:
State Tax: applicable to all customers without resale ID but only in Florida, Washington and California.
Federal Excise Tax: applicable to a group of customers that buy products for medical applications; not applicable to the same group of customers who also may purchase products for non-medical applications. And if a customer in this group is from FL, WA or CA, then they are subject to State for all products and Federal for medical products only.

In the set up of the State tax (which is set up correctly and works fine) I learned that no tax will be calculated if the customer does not have a Tax liability assigned to the customer account. I attempted to add in the federal by adding a second rate of Tax exempt to an existing liability, but could not get it to calculate properly. I would greatly appreciate any advice or assistance from anyone who has mastered the Epicor tax set up. Or, perhaps someone may be aware of documentation or a guide that can provide a better understanding of how to set up varying rates as I described?