Installed your module worked fine until I made a mistake in adding another Tax class Zone.
Tax rate not calculated correctly (Standard)
I have 2 Tax Rate Classes and are in different zones.
By mistake or just lazy I gave them the same description. After that the tax calculation (Standard) did not work correctly. After reviewing the code I noticed that the sql retrieves tax rates based on the descrition in the table . So I fixed the descriptions (made them different) and now get only one tax rate (for my needs) and it works totally correct.
I did notice some others are having a similar problem and may be what I did wrong
Again thanks for a great module.