Rounding a Sum

I have a BIP report that shows the following for grand totals.

This is almost correct. The total should be 6538.58 but I am getting 6538.57.  I am not able to figure out what round command I want to use. 

This is the properties of this field as is..

<?sum(GROSS)?>

I have tried

<?xdofx:round(sum(GROSS),2)?> get an error. 

I have tried

<?round(sum(GROSS))?> and get 6539.  That makes sense to me but not the number that I want. 

What am I missing?  Any help is most appreciated.  This seems like it should be more simple than this.  :-)

Thanks!