The help of this opencart module you can set opencart product tax based on different customer group and guest user also.
=======================installation=======================
* This is an OCMOD extension, simply upload with extension installer.
* Go to "system - settings >store> edit > option" and select the customer groups under the Taxes section.
* Uses OpenCart's built-in module system (no core files are overwritten).
* Excellent & Best Support.