protected function _calcBasketTotalDiscount()
    {
        if ($this->_oTotalDiscount === null || (!$this->isAdmin())) {
            $this->_oTotalDiscount = $this->_getPriceObject();

            if (is_array($this->_aDiscounts)) {
                foreach ($this->_aDiscounts as $oDiscount) {
                    // skipping bundle discounts
                    if ($oDiscount->sType == 'itm') {
                        continue;
                    }

                    // add discount value to total basket discount
                    $this->_oTotalDiscount->add($oDiscount->dDiscount);
                }
            }
        }
    }