What setup is required to ignore Tax Classification code and instead use the Tax Rules for the AR In

Most of our AR billing is Project related. Currenly users are using Tax Classification Codes (TCC) to derive the Taxes during projects to AR interface. We want to change this tax determination based on the TCC. Instaed we want to ignore the TCC and use the Rules defined in the ebtax to derive the taxes. Please let me know if there is any documentation around this. Thanks. Muin