Magento Upgrade problem - After upgrade from magento v 1.5 to 1.7.0.2 Grand total issue

Add the below code in

app/code/core/Mage/Tax/Model/Sales/Total/Quote/Tax.php


Line Number : 146  $this->_processHiddenTaxes();

$address->setGrandTotal($address->getGrandTotal() + $address->getTaxAmount());
$address->setBaseGrandTotal($address->getBaseGrandTotal() + $address->getBaseTaxAmount());


Thats it clear your magento cache and browser cache ,check its working :)

Hope this help for solve upgrading issues

Refer : http://www.magentocommerce.com/boards/viewthread/290928/