You can view the giving history of the entire Current Group. If you are looking at a contact's MPD tab, you see the graph in the lower right showing their giving history. If you press the Group button in that screen, TntMPD will compile the giving history for ALL contacts in the Group list.
The default view on the MPD Tab is the giving for the selected contact (above). The same MPD Tab after you press the Group button (below).
