Hi Vijay,
In the earlier replies of this thread there is a link to the document by Neha on how to perform Currency Conversion.
You can also refer to another document http://scn.sap.com/docs/DOC-40812 which explains how to perform Dynamic currency conversion.
As you can see, the feature is already provided by HANA. You do not need to perform any conversion explicitly.
Hope this helps.
Regards,
Ravi