[FIXED] PrestaShop 1.2.4 price calculation issue

[Matthieu Biart]

Hi everyone!

You're numerous to have noticed that the last PrestaShop stable release have rounding issues concerning prices.
So here is a summary about the situation and what we're planing to do to solve it as fast as possible.

Issue:
The PrestaShop conception imposes to use 6 digits in price calculation*.
That implies an important precision about ordered products (shopping cart, BO & FO order detail/history, emailed order detail and the PDF invoice).
Unfortunately in some case, some customers may have encounter a difference (around a ¤0.01) between the sale price and the real (billing) price (e.g., $123.22 instead of $123.21).

Solution:
1. Solution explanation: Please have a look just below to see the new display method.
2. Solution validation: The solution provided is not yet validated by any accountant. So as soon as we get a validation we will proceed to the implementation.
3. Implementation: Implementation on the SVN
4. New beta release: In order to test it before using it in live shop
5. Stable release: if this new method is correct a new stable version will be release and you'll be able to fix all your live shops.

Solution explanation:
We propose two different behaviors configurable via the Back Office.
1. All summaries will display detailed product prices TAX EXCLUDED.
Of course there will be a tax included total and a complete price breakdown.
2. All summaries will display detailed product prices TAX INCLUDED.
And again a tax excluded total and a complete price breakdown.
To those new behavior comes a new feature allowing you to set them for each customer group (which will allow you to display differently when you sell to professional).

*6 digits are required in order to display rouded-up to the nearest dollar/euro/... tax included prices. e.g., $15.00, 45.00 €

PS: There is another price miscalculation issue related to the discount quantity feature. But there are no relation between them. Even if we will also fix this issue for the next release.

Update:
The fix for this issue has been implemented on the first 1.3 public version known as PrestaShop 1.3 alpha 1 (1.3.0.1).
Therefore, it is available on all newer releases, meanings PrestaShop >= 1.3.x
As explained above, if you want to correct your live shop you must wait for the final 1.3 version.
In deed the whole PrestaShop price calculation method has been recoded in order to fix this issue and a patch is not viable.