The StrikeIron service provides access to live sales and use tax data using a U.S. ZIP or Canadian postal code. Receive the general sales and use tax and shipping rate levels for the state, county, and city for over 19,000 U.S. and Canadian tax jurisdictions.
Please find more informartion about how to install plugins here.
The plugin is provided absolutely for free and includes source code. Find the project Github repository here.