[Done v1.3.9] tax calculation

[hugo13]

given:
zc138
tax == 19%
price with tax == 9.99
result == 10.00

because the function zen_add_tax() "double rounds" the value

return zen_round($price, $currencies->currencies[DEFAULT_CURRENCY]['decimal_places']) + zen_calculate_tax($price, $tax); 

8.40 + 1.60 == 10.00


i think it should be

        $tax = $price * $tax / 100;
        $priceInclTax = $price + $tax;
        $priceInclTaxFormatted = zen_round($priceInclTax, $currencies->currencies[DEFAULT_CURRENCY]['decimal_places']);
        return $priceInclTaxFormatted; 

8.395 + 1.59505 = 9.99005 ==> 9.99

[Revenant]

Absolutely correct , just the problem I was looking for has been solved.

Strange no one else noticed this....thanks man!

[Marco_K]

In which file I need to change this?

[hugo13]

In which file I need to change this?

/includes/functions/functions_taxes.php

[Marco_K]

Didn't work for me. I use 1.3.8.
TAX 19% €10,099 was rounded off at €10,11

[hugo13]

MY VALUES: ( http://demo.zen-cart.at/index.php?ma...roducts_id=184 )

Products Price (Net): 53.1526
Products Price (Gross): 63.2516
Tax: 19%

==> shopdisplay
€53.15 Sub-Total:
€0.00 Store Pickup (Walk In):
€10.10 19%:
€63.25 Total:

and YOUR VALUES ?

[Marco_K]

Currencie with 2 numbers after the comma:
Sub-Total: €14,90
Transport: €7,50
Tax 19%: €4,27
Total: €26,67


Currencie with 3 numbers after the comma:
Sub-Total: €14,900
Transport: €7,500
Tax 19%: €4,256
Total: €26,656

[Marco_K]

/includes/functions/functions_taxes.php

Maybe you can send me your /includes/functions/functions_taxes.php file ?

Let's see what happens when i overwrite my one (making a backup first).

[Marco_K]

I think i've got it (EUREKA) ;-)

This is what my code looks like now, Line 160 til 180, in /includes/functions/functions_taxes.php:

// Add tax to a products price based on whether we are displaying tax "in" the price
  function zen_add_tax($price, $tax) {
    global $currencies;
    if ( (DISPLAY_PRICE_WITH_TAX == 'true') && ($tax > 0) ) {
              $tax = $price * $tax / 100;
        $priceInclTax = $price + $tax;
        $priceInclTaxFormatted = zen_round($priceInclTax, $currencies->currencies[DEFAULT_CURRENCY]['decimal_places']);
        return $priceInclTaxFormatted;
    } else {
      return zen_round($price, $currencies->currencies[DEFAULT_CURRENCY]['decimal_places']);
    }
  }

// Calculates Tax rounding the result
  function zen_calculate_tax($price, $tax) {
    global $currencies;
    $result = bcmul($price, $tax, $currencies->currencies[DEFAULT_CURRENCY]['decimal_places']);
    $result = bcdiv($result, 100, $currencies->currencies[DEFAULT_CURRENCY]['decimal_places']);
    return $result;
    return zen_round($price * $tax / 100, $currencies->currencies[DEFAULT_CURRENCY]['decimal_places']);
  } 

Tax 19% €4,256 is now rounded off at €4,26 and NOT €4,27

[hugo13]

I think, the php-function round is buggy ( http://php.net/manual/de/function.round.php see the comments and workarounds: setting of type, doesnt helped)

bcmul & co is problematic, because php must be compiled with --enable-bcmath

the only working way was to change the function zen_round (includes/functions/function_general.php)

  function zen_round($number, $precision) {
/// fix rounding error on GVs etc.
    $number = round($number, $precision+1);   // round with a higher prec
    $number = round($number, $precision);

    return $number;
  } 

the second helping way was:
settype($tax, 'string);
if I set it to "float" its also wrong
its a bit crazy