title: Magento custom cart/checkout values get reset on "Place Order"
body: <p>We are using Magento Enterprise 1.10 and have been implementing a custom way to provide free shipping and no taxes on specific products. I have successfully implemented the display part of this in cart and in Onepage checkout (step 5). The issue I am having is when you we click "Place Order" it erases (or resets) the custom values for subTotal, grandTotal and taxAmount. I can see in the sales_flat_quote and sales_flat_quote_item tables that the values are being set with the custom values I have given it. But the grandTotal and taxAmount in the sales_flat_quote_address table aren't being set properly (not sure if this is related, but assuming). They are being re-calculated the default way Magento calculates them. </p>
  
  <p>So for example I might setTaxAmount a custom value of say $20. But Magento takes the product price and the tax percentage and recalculates it. If that makes sense.</p>
  
  <p>I have pinpointed that in our OnepageController.php in the method saveOrderAction()</p>
  
  <pre><code>if ($data = $this-&gt;getRequest()-&gt;getPost('payment', false)) {
     $this-&gt;getOnepage()-&gt;getQuote()-&gt;getPayment()-&gt;importData($data);
  }
  </code></pre>
  
  <p>This section of code is replacing the custom values I've set with with how Magento normally sets them in:</p>
  
  <p>My questions is there any why to prevent the above block of code from recalculating the values and just use the values I've already set in:</p>
  
  <pre><code>Mage::getSingleton('checkout/session')-&gt;getQuote()
  </code></pre>
  
  <p>Thanks in advance,</p>