Create a new table that groups values from an existing table?

I have a sales table and want to create a new table that groups the sales table by salesman and customer, summing sales_ammount.  
I know how to do this in SQL, but I want to do it in PowerBI since my dashboard uses filters on the sales table.  
To clarify, my sales table is like this:

And I want a new Salesman and Customer ammounts to look like this:

How could I accomplish this in powerBI? I have been trying to use DAX to define a new table (specifically the "Table.Group" function but I can't get it to work.  Thanks!