Hey vits
One method is to feed the departments used into a @Parameter List and then pipe them into the {REPORT ORDER DETAILS:x} tag:
@{REPORT TICKET DETAILS:T.Department,T.TotalAmount.sum::{0}:,}
>Dept: $1
{REPORT ORDER DETAILS:O.User,O.ExactTotal.Sum:(DE=$1):{0}|${1}:}
That above is user sales per department.
I have not used tags much so no help there.