$discount = (float) ($calc_totals - $order->get_total());
if ( round($discount,2) > 0.00  ) {
    $line_items[] = array('type' => 7, 'price' => -$discount, 'title' => 'Discount', 'description' => 'WooCommerce Coupon Code');
    $calc_totals -= $discount;
}