Hi Sonia
As mentioned above by Dan agree with that.
Need to define a rounding method for currency translation. There are three different types available in sap help.
Please find attached reference link.
http://help.sap.com/saphelp_sem60ep1/helpdata/en/79/54723b954df67fe10000000a114084/content.htm
If the method is already existed pleased check the settings/configuration.
Regards
Rajesh SVN