Step1: Getting the SubTotal of the Cart:
<?php Mage::getSingleton('checkout/session')->getQuote()->getSubtotal(); ?>
Step2: Getting the GrandTotal of the Cart:
<?php
$totals = Mage::getSingleton('checkout/session')->getQuote()->getTotals(); //Total object
$grandtotal = round($totals["grand_total"]->getValue());//Grandtotal value
echo $formattedPrice = Mage::helper('core')->currency($grandtotal , true, false);
?>