I have a custom attribute added to the customer model indicating weather we want to apply the tax or not. That attribute returns a boolean. I want to intercept in the way of where magento applies tax rules to the quote object & remove the tax rules if the attribute is set.
As far as i could understand
Mage_Tax_Model_Sales_Total_Quote_Tax::collect is the one responsible for calculating taxes & setting them onto quote object. I think re-writing it might be able to somehow exclude that quote from taxes. but don't know how to proceed from here.
Also maybe the event
sales_quote_collect_totals_after called from inside
Mage_Sales_Model_Quote::collectTotals should be able to work. These events pass on the quote object itself. But again i don't know how to proceed.