Quantity and Value Summation Line to the header for non USD currency values causes variance

Summary:

Quantity and Value Summation Line to the header for non USD currency values on the header causes variance

Content (please ensure you mask any confidential information): if we sum up a value qualifier from the header to the line for a non usd currency then the systems converts it to usd and then again reconverts it back to the declaration currency, this cause some variance in the calculation.

The system should simply add the values of all the lines to the header irrespective of the currency i.e. EUR or INR or USD.

Is this the standard behaviour and do we have any logic configs or property which can help eliminate the variance.