This is how we resolved the problem of taxes being added to the cart for new users who had not yet entered a shipping address. The problem occurs because the taxes are based on the default warehouse's address. This approach is only for 7.0.2 (and before?) since 7.0.3 gives you the option to correct this directly.
In our drop ship environment, we don't use integrated shipping. So its address isn't critical. We just updated the database directly from SQL to make the Province NULL. No state code means the in-state tax rules aren't applied and no tax line is added. Once the user adds an address, all is fine.
It does mean your address on some emails and printed invoices won't have your state listed. But since we didn't null out the postal code, they can always look it up directly. I don't know if integrated shipping would still work with just the zip code but someone may want to find out.
If anyone knows of potential problems with this approach, please let us know. Thanks.
ZLA