- Created backwards compatible changes.

- Deprecated old function with hard coded precision.

Author: dverkade

app/code/Magento/Directory/Model/PriceCurrency.php

@@ -62,7 +62,7 @@ public function convert($amount, $scope = null, $currency = null)
      */
     public function convertAndRound($amount, $scope = null, $currency = null, $precision = self::DEFAULT_PRECISION)
     {
-        return $this->round($this->convert($amount, $scope, $currency), $precision);
+        return $this->roundPrice($this->convert($amount, $scope, $currency), $precision);
     }
 
     /**
@@ -148,7 +148,15 @@ protected function getStore($scope = null)
     /**
      * {@inheritdoc}
      */
-    public function round($price, $precision = self::DEFAULT_PRECISION)
+    public function round($price)
+    {
+        return round($price, 2);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function roundPrice($price, $precision = self::DEFAULT_PRECISION)
     {
         return round($price, $precision);
     }

lib/internal/Magento/Framework/Pricing/PriceCurrencyInterface.php

@@ -78,11 +78,20 @@ public function convertAndFormat(
     /**
      * Round price
      *
+     * @deprecated
+     * @param float $price
+     * @return float
+     */
+    public function round($price);
+
+    /**
+     * Round price with precision
+     *
      * @param float $price
      * @param int $precision
      * @return float
      */
-    public function round($price, $precision = self::DEFAULT_PRECISION);
+    public function roundPrice($price, $precision = self::DEFAULT_PRECISION);
 
     /**
      * Get currency model