It's a little unclear what the data is you are working with. Do you need to sum the {table.totalsales} field in order to get the total per salesperson? Or is {table.totalsales} already a sum by salesperson? If we assume that it needs to be summed by salesperson and then you have to determine which salesperson's total is the highest, you could just do a TopN on the summary field and select 1 as N.
If {table.totalsales} is already a sum by salesperson, then you could do a group select to bring back only the record with the highest sales amount and corresponding salesperson:
{table.totalsales} = maximum(table.totalsales}
-LB