Issue in FM CONVERT_TO_LOCAL_CURRENCY

Hi Experts,

I am using FM CONVERT_TO_LOCAL_CURRENCY for currency conversion in my program. When i am using this FM to convert value from YEN to WON ,it gives me correct value but when i try to convert value from USD to WON , it gives me value with difference in decimals and I am using BAPI_CURRENCY_CONV_TO_EXTERNAL to convert it into external format after which i am getting correct value. Can anybody tell me whether FM CONVERT_TO_LOCAL_CURRENCY handles conversion to SAP external display for certain currencies and for certain currencies we have to explicitly convert it into external format?