diff --git a/includes/abstracts/abstract-wc-order.php b/includes/abstracts/abstract-wc-order.php
index e5e55e84445..c5ce6ce533c 100644
--- a/includes/abstracts/abstract-wc-order.php
+++ b/includes/abstracts/abstract-wc-order.php
@@ -1483,14 +1483,21 @@ abstract class WC_Abstract_Order extends WC_Abstract_Legacy_Order {
 			$this->calculate_taxes();
 		}
 
-		// Sum taxes.
+		// Sum taxes again so we can work out how much tax was discounted. This uses original values, not those possibly rounded to 2dp.
 		foreach ( $this->get_items() as $item ) {
-			$cart_subtotal_tax += $item->get_subtotal_tax();
-			$cart_total_tax    += $item->get_total_tax();
+			$taxes = $item->get_taxes();
+
+			foreach ( $taxes['total'] as $tax_rate_id => $tax ) {
+				$cart_total_tax += (float) $tax;
+			}
+
+			foreach ( $taxes['subtotal'] as $tax_rate_id => $tax ) {
+				$cart_subtotal_tax += (float) $tax;
+			}
 		}
 
 		$this->set_discount_total( $cart_subtotal - $cart_total );
-		$this->set_discount_tax( $cart_subtotal_tax - $cart_total_tax );
+		$this->set_discount_tax( wc_round_tax_total( $cart_subtotal_tax - $cart_total_tax ) );
 		$this->set_total( round( $cart_total + $fee_total + $this->get_shipping_total() + $this->get_cart_tax() + $this->get_shipping_tax(), wc_get_price_decimals() ) );
 
 		do_action( 'woocommerce_order_after_calculate_totals', $and_taxes, $this );