title: Bug discount and total price PrestaShop
body: <p>I have a PrestaShop 1.6.1.1 connected with an ERP.</p>
  
  <p>Recently, we have a customer with a specific group (with -5% discount) on all products. At his last order, discount did not work ...</p>
  
  <p>So, I did lot of tests. I duplicate his account then did order process and discounts works perfectly. Sometimes, when I go on product-list, discounts not showing, if I press F5 (refresh), they appear ...</p>
  
  <ul>
  <li>Is there anyone know where is the problem?</li>
  <li>Cache problem?</li>
  <li>If yes, how to resolve it? </li>
  </ul>
  
  <p>Another problem, sometimes, there are price difference of 0,01€ between PrestShop and ERP or when I check order email, and when I make the sum of product prices, not the same than total.</p>
  
  <p>For example, prestashop will show 237,67€ instead of 237,66€</p>
  
  <p><a href="https://i.stack.imgur.com/rRl9K.png" rel="nofollow noreferrer">Screenshot of price difference here</a></p>
  
  <p>My configuration of prestashop :</p>
  
  <p>• Round mode : Round up away from zero, when it is half way there (recommended)</p>
  
  <p>• Round type : Round on the total</p>
  
  <p>• Number of decimals. : 2</p>
  
  <p>Thanks for your replies !</p>