Получение элементов корзины со скидками - amel-post/bitrix.help GitHub Wiki
$basket = \Bitrix\Sale\Basket::loadItemsForFUser(
\Bitrix\Sale\Fuser::getId(),
\Bitrix\Main\Context::getCurrent()->getSite()
);
global $USER;
$registry = \Bitrix\Sale\Registry::getInstance(\Bitrix\Sale\Registry::REGISTRY_TYPE_ORDER);
/** @var \Bitrix\Sale\Order $orderClass */
$orderClass = $registry->getOrderClassName();
$order = $orderClass::create(\Bitrix\Main\Context::getCurrent()->getSite(), $USER->GetID());
$result = $order->appendBasket($basket);
$discounts = $order->getDiscount();
$showPrices = $discounts->getShowPrices();