You can customize tax rates in your Zoho CRM account by following the steps given below:

1. Log in to Zoho CRM with Administrator privileges.
   
2. Click Setup > Customization > Fields.
3. Select Products  Module from the drop-down list.
4. Click Customize Tax Rates.
5. In the Customize Tax Rates page, click the Add Tax link.
6. Specify the type of tax and tax rate in Tax Label and Tax Value fields respectively.
7. Click Save.

Note: By default, only two decimal values can be included. You cannot customize the tax rate’s decimal value.