title: Magento tax rounding issue
body: <p>I got strange rounding issue for VAT in Magento. My product set up is
   * product price incl 20% VAT is 183.59</p>
  
  <p>I added 30 items into basket and it would cost 30 * 183.59 = 5507.70. I can see this value in basket/checkout so that's fine. If I have just 1 item in basket it's ok.</p>
  
  <p>Also the final VAT would be 5507.70 * 20 / 120 = 917.95, but I'm getting 918.00</p>
  
  <p>Do you have any idea how to fix this or where would I take a look? Thanks in advance.</p>