The KampData TaxEngine is a plug in product that brings sales tax related features to other applications. If you create or are able to modify an order entry application that integrates with Microsoft Dynamics GP then you can enable the KD TaxEngine's features in that application.
The KD TaxEngine is a .NET DLL written in C# that presents an Application Programming Interface (API). As an API, the KD TaxEngine's features can be utilized inside other .NET and/or COM enabled applications.