diff --git a/app/code/core/Mage/Tax/Model/Config.php b/app/code/core/Mage/Tax/Model/Config.php
index 4f9bc3f0a9d30..1ff2e1814b26e 100644
--- a/app/code/core/Mage/Tax/Model/Config.php
+++ b/app/code/core/Mage/Tax/Model/Config.php
@@ -91,6 +91,11 @@ class Mage_Tax_Model_Config
      */
     protected $_needUsePriceExcludeTax = false;
 
+    /**
+     * @var $_priceIncludeTax bool
+     */
+    protected $_priceIncludeTax = null;
+
     /**
      * Flag which notify what we need use shipping prices exclude tax for calculations
      *
@@ -114,7 +119,23 @@ public function priceIncludesTax($store=null)
         if ($this->_needUsePriceExcludeTax) {
             return false;
         }
-        return (bool)Mage::getStoreConfig(self::CONFIG_XML_PATH_PRICE_INCLUDES_TAX, $store);
+        if ($this->_priceIncludeTax === null) {
+            $this->_priceIncludeTax = (bool)Mage::getStoreConfig(
+                self::CONFIG_XML_PATH_PRICE_INCLUDES_TAX,
+                $store
+            );
+        }
+        return $this->_priceIncludeTax;
+    }
+
+    /**
+     * Declare prices type
+     * @param bool $flag
+     */
+    public function setPriceIncludeTax($flag)
+    {
+        $this->_priceIncludeTax = $flag;
+        return $this;
     }
 
     /**