How to get the Grand Total with shipping charge and tax at onepage checkout in Magento 1.9?

Try

$quote = Mage::getModel('checkout/session')->getQuote();
$quoteData= $quote->getData();
$grandTotal=$quoteData['grand_total'];

OR

print_r(Mage::helper('checkout')->getQuote()->getData());

You can get the grand total by using this:

$grandTotal = Mage::getModel('checkout/session')->getQuote()->getGrandTotal();