Setting Counties in US that have multiple tax rates

We are manually configuring EBTAX based on rates from a 3rd party (not vertex or taxware).  We are mapping State, Counties, and Cities to geographies in the system.  We are loading our tax juridictions and rates directly through custom load program.  However, we are running into an issue with respect to how to setup county tax jurisdictions in US where there are multiple county sales tax rates depending on the city juridisdiction.  When loading our tax jurisdictions we are mapping a jurisdiction to geography - however, Oracle will not allow you to setup a tax jurisdiction and assign a geography that