title: Magento applies tax on product prices that already including tax
body: <p>I've added products prices with tax included (in the field Price [EUR] [ Including Tax]) 
  Now when I put a product in the cart, Magento applies the tax to price that already including the tax!</p>
  
  <p><em>Example</em>: if the product has "Price [EUR] [ Including Tax]"=100€ in the cart I have:</p>
  
  <blockquote>
    <p>Product price  € 100</p>
    
    <p>Sub total     € 100</p>
    
    <p>Taxes     € 20</p>
    
    <p>Totale  €120 (but the correct price including taxes is 100€!)</p>
  </blockquote>
  
  <p>instead I want this:</p>
  
  <blockquote>
    <p>Product price  € 100</p>
    
    <p>Sub totale     € 80</p>
    
    <p>Taxes     € 20</p>
    
    <p>Total  €100</p>
  </blockquote>
  
  <p>I'v tried all the settings and I'm going mad! is there a solution?</p>