MAGETWO-90971: Error is returned when customer checks out with multiple addresses

Author: rganin

app/code/Magento/Tax/Model/Plugin/OrderSave.php

@@ -80,8 +80,10 @@ protected function saveOrderTax(\Magento\Sales\Api\Data\OrderInterface $order)
         $ratesIdQuoteItemId = [];
         foreach ($taxesForItems as $taxesArray) {
             foreach ($taxesArray['applied_taxes'] as $rates) {
-                if (isset($rates['extension_attributes']['rates'])) {
-                    $taxRates = $rates['extension_attributes']['rates'];
+                if (isset($rates['extension_attributes'])) {
+                    $taxRates = $rates['extension_attributes'] instanceof OrderTaxDetailsAppliedTaxExtension
+                        ? $rates['extension_attributes']->getRates()
+                        : $rates['extension_attributes']['rates'];
                     if (is_array($taxRates)) {
                         if (count($taxRates) == 1) {
                             $ratesIdQuoteItemId[$rates['id']][] = [