Magento + TaxJar Custom Product Taxability Exceptions by State

Smartcalcs.php

<?php

// Include around here:
// https://github.com/taxjar/taxjar-magento-extension/blob/master/app/code/community/Taxjar/SalesTax/Model/Smartcalcs.php#L236

// Taxable in one state, exempt in other exempt states
$specialTaxableProducts = array(1001, 1002, 1003, 1004); // Product IDs
 
// Tax these clothing products if shipped to PA
if (in_array($item->getProductId(), $specialTaxableProducts) && $address->getRegionCode() == 'PA') {
     $taxCode = ''; // Fully taxable
}

// Taxable in multiple states, exempt in other exempt states
$specialTaxableProducts = array(1001, 1002, 1003, 1004); // Product IDs
$specialTaxableStates = array('MN', 'PA');
 
// Tax these Clothing products if shipped to MN or PA
if (in_array($item->getProductId(), $specialTaxableProducts) && in_array($address->getRegionCode(), $specialTaxableStates)) {
     $taxCode = ''; // Fully taxable
}