diff --git a/CHANGELOG.md b/CHANGELOG.md
index db68d6a985..a9443676af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Fixed a PHP error that could occur when calculating order totals. ([#3802](https://github.com/craftcms/commerce/issues/3802)) 
 - Fixed a bug where a product’s default price was showing incorrectly on the Products index page. ([#3807](https://github.com/craftcms/commerce/issues/3807))
 - Fixed a bug where inline-editable Matrix fields weren’t saving content on product variants. ([#3805](https://github.com/craftcms/commerce/issues/3805))
 - Fixed a bug where order errors weren't showing on the Edit Order page.
diff --git a/src/elements/Order.php b/src/elements/Order.php
index 19870f64c9..63ed535063 100644
--- a/src/elements/Order.php
+++ b/src/elements/Order.php
@@ -1700,7 +1700,8 @@ public function updateOrderPaidInformation(): void
         $justPaid = $paidInFull && $this->datePaid == null;
         $justAuthorized = $authorizedInFull && $this->dateAuthorized == null;
 
-        $canComplete = ($this->getTotalAuthorized() + $this->getTotalPaid()) > 0;
+        $completeTotal = $this->_getTeller()->add($this->getTotalAuthorized(), $this->getTotalPaid());
+        $canComplete = $this->_getTeller()->greaterThan($completeTotal, 0);
 
         // If it is no longer paid in full, set datePaid to null
         if (!$paidInFull) {
@@ -2662,7 +2663,7 @@ public function getPaidStatusHtml(): string
      */
     public function getTotal(): float
     {
-        return Currency::round($this->getItemSubtotal() + $this->getAdjustmentsTotal());
+        return (float)$this->_getTeller()->add($this->getItemSubtotal(), $this->getAdjustmentsTotal());
     }
 
     /**
@@ -2670,18 +2671,19 @@ public function getTotal(): float
      */
     public function getTotalPrice(): float
     {
-        $total = $this->getItemSubtotal() + $this->getAdjustmentsTotal(); // Don't get the pre-rounded total.
+        $total = (float)$this->_getTeller()->add($this->getItemSubtotal(), $this->getAdjustmentsTotal());
+        // Don't get the pre-rounded total.
         $strategy = $this->getStore()->getMinimumTotalPriceStrategy();
 
         if ($strategy === Store::MINIMUM_TOTAL_PRICE_STRATEGY_ZERO) {
-            return Currency::round(max(0, $total));
+            return (float)$this->_getTeller()->max(0, $total);
         }
 
         if ($strategy === Store::MINIMUM_TOTAL_PRICE_STRATEGY_SHIPPING) {
-            return Currency::round(max($this->getTotalShippingCost(), $total));
+            return (float)$this->_getTeller()->max($this->getTotalShippingCost(), $total);
         }
 
-        return Currency::round($total);
+        return $total;
     }
 
     public function getItemTotal(): float
diff --git a/src/models/LineItem.php b/src/models/LineItem.php
index ddd3938ee1..a671fc2c2f 100755
--- a/src/models/LineItem.php
+++ b/src/models/LineItem.php
@@ -703,7 +703,8 @@ public function getSubtotal(): float
      */
     public function getTotal(): float
     {
-        return $this->getSubtotal() + $this->getAdjustmentsTotal();
+        $teller = Plugin::getInstance()->getCurrencies()->getTeller($this->order->currency);
+        return (float)$teller->add($this->getSubtotal(), $this->getAdjustmentsTotal());
     }
 
     /**