I can create a tax rule for 4.225% sales tax. It will save correctly and display correctly in the tax rules list. But if you edit it, the tax rate is only shown with two decimal places and shows as 4.23%. If you don't realize it's changed (and the only way to check is to cancel and see what it says in the list), it will get saved with only the two decimal places.
The fix is to change the formatting to F4 in Admin/Taxes/EditTaxRule.aspx.cs and Admin/Orders/Edit/EditOrderItems.
BUG: Edit Tax Rule - Decimal Places
Re: BUG: Edit Tax Rule - Decimal Places
An issue have been logged for reported problem, you can track progress here
http://bugs.ablecommerce.com/show_bug.cgi?id=8152
http://bugs.ablecommerce.com/show_bug.cgi?id=8152