protected function calculate_discounts() {
		$this->get_coupons_from_cart();

		$discounts = new WC_Discounts( $this->cart );

		// Set items directly so the discounts class can see any tax adjustments made thus far using subtotals.
		$discounts->set_items( $this->items );

		foreach ( $this->coupons as $coupon ) {
			$discounts->apply_coupon( $coupon );
		}

		$coupon_discount_amounts     = $discounts->get_discounts_by_coupon( true );
		$coupon_discount_tax_amounts = array();

		// See how much tax was 'discounted' per item and per coupon.
		if ( $this->calculate_tax ) {
			foreach ( $discounts->get_discounts( true ) as $coupon_code => $coupon_discounts ) {
				$coupon_discount_tax_amounts[ $coupon_code ] = 0;

				foreach ( $coupon_discounts as $item_key => $coupon_discount ) {
					$item = $this->items[ $item_key ];

					if ( $item->product->is_taxable() ) {
						// Item subtotals were sent, so set 3rd param.
						$item_tax = wc_round_tax_total( array_sum( WC_Tax::calc_tax( $coupon_discount, $item->tax_rates, $item->price_includes_tax ) ), 0 );

						// Sum total tax.
						$coupon_discount_tax_amounts[ $coupon_code ] += $item_tax;

						// Remove tax from discount total.
						if ( $item->price_includes_tax ) {
							$coupon_discount_amounts[ $coupon_code ] -= $item_tax;
						}
					}
				}
			}
		}

		$this->coupon_discount_totals     = (array) $discounts->get_discounts_by_item( true );
		$this->coupon_discount_tax_totals = $coupon_discount_tax_amounts;

		if ( wc_prices_include_tax() ) {
			$this->set_total( 'discounts_total', array_sum( $this->coupon_discount_totals ) - array_sum( $this->coupon_discount_tax_totals ) );
			$this->set_total( 'discounts_tax_total', array_sum( $this->coupon_discount_tax_totals ) );
		} else {
			$this->set_total( 'discounts_total', array_sum( $this->coupon_discount_totals ) );
			$this->set_total( 'discounts_tax_total', array_sum( $this->coupon_discount_tax_totals ) );
		}

		$this->cart->set_coupon_discount_totals( wc_remove_number_precision_deep( $coupon_discount_amounts ) );
		$this->cart->set_coupon_discount_tax_totals( wc_remove_number_precision_deep( $coupon_discount_tax_amounts ) );

		// Add totals to cart object. Note: Discount total for cart is excl tax.
		$this->cart->set_discount_total( $this->get_total( 'discounts_total' ) );
		$this->cart->set_discount_tax( $this->get_total( 'discounts_tax_total' ) );
	}