title: Get tax_calculation_rule_id from Tax class in magento
body: <p>How can i get the <code>tax_calculation_rule_id</code> if i have product tax class and customer tax class. Currently i am working on a module in which i am trying to extend magento API's for tax rules. I have <code>customer tax class name</code> and <code>product class name</code>, Is there any function which can give me <code>tax_calculation_rule_id</code> on the basis of these two</p>