Sum with Grouping

Are the groups static, or do they need to be dynamic based on a user selection?

If they're static, it's easy. Make a new field (preferably at your data source if you can, else in a query (e.g. in Power Query) before the data is added to the Power Pivot model) with those groups. Then you can just create visualizations against the new field that contains the group.

If they must be dynamic based on user selection, you'll have to give us some more detail on what your expected use case is, and the solution will be a bit more complex.