This fixes an calculation issue with promo codes.

Magento calculates the totals when using a promo code with less than cent values.
Whenever this is a case, the $total variable could be something like
$total === 19.241. This value multiplied by 100 for the frontend could lead to
wrong frontend values. The invoice value below the banner is 100 times higher than
it should be.
Merge pull request #1 from dabio/calculations-with-promo-codes

This fixes an calculation issue with promo codes.