MAGETWO-51868: [Github] USPS shipping weight calculation rounds ounces to whole number

- Added private static variable

Author: rliukshyn

app/code/Magento/Usps/Model/Carrier.php

@@ -67,6 +67,13 @@ class Carrier extends AbstractCarrierOnline implements \Magento\Shipping\Model\C
      */
     protected $_code = self::CODE;
 
+    /**
+     * Weight precision
+     *
+     * @var int
+     */
+    private static $weightPrecision = 10;
+
     /**
      * Rate request data
      *
@@ -324,7 +331,7 @@ public function setRequest(\Magento\Quote\Model\Quote\Address\RateRequest $reque
 
         $weight = $this->getTotalNumOfBoxes($request->getPackageWeight());
         $r->setWeightPounds(floor($weight));
-        $r->setWeightOunces(round(($weight - floor($weight)) * self::OUNCES_POUND, 10));
+        $r->setWeightOunces(round(($weight - floor($weight)) * self::OUNCES_POUND, self::$weightPrecision));
         if ($request->getFreeMethodWeight() != $request->getPackageWeight()) {
             $r->setFreeMethodWeight($request->getFreeMethodWeight());
         }
@@ -371,7 +378,7 @@ protected function _setFreeMethodRequest($freeMethod)
 
         $weight = $this->getTotalNumOfBoxes($r->getFreeMethodWeight());
         $r->setWeightPounds(floor($weight));
-        $r->setWeightOunces(round(($weight - floor($weight)) * self::OUNCES_POUND, 10));
+        $r->setWeightOunces(round(($weight - floor($weight)) * self::OUNCES_POUND, self::$weightPrecision));
         $r->setService($freeMethod);
     }