если валюта в магазине одна - пробуй так:
...
public function addOrder($data) {
...
foreach ($data['products'] as $product) {
$this->db->query("INSERT INTO " . DB_PREFIX . "order_product SET order_id = '" . (int)$order_id . "', product_id = '" . (int)$product['product_id'] . "', name = '" . $this->db->escape($product['name']) . "', model = '" . $this->db->escape($product['model']) . "', quantity = '" . (int)$product['quantity'] . "', price = '" . (float)$product['price'] . "', total = '" . (float)$product['total'] . "', tax = '" . (float)$product['tax'] . "', reward = '" . (int)$product['reward'] . "'");
...>>
...
public function addOrder($data) {
...
foreach ($data['products'] as $product) {
$this->db->query("INSERT INTO " . DB_PREFIX . "order_product SET order_id = '" . (int)$order_id . "', product_id = '" . (int)$product['product_id'] . "', name = '" . $this->db->escape($product['name']) . "', model = '" . $this->db->escape($product['model']) . "', quantity = '" . (int)$product['quantity'] . "', price = '" . (float)$product['price'] . "', total = '" . (float)$product['total'] . "', tax = '" . (float)$product['tax'] . "', reward = '" . (($data['totals'][(count($data['totals'])-1)]['code'] == 'total') && ($data['totals'][(count($data['totals'])-1)]['value'] >= 'общая сумма заказа (с доставкой и прочим), начиная с которой бонусы будут начисляться')) ? (int)$product['reward'] : 0 . "'");
...