Usually that sort of "merge" queries are not a good practice. Just remember
a query is not just an spreadsheet.[Think if you can get the desired result
using calculated fields on a report].
However, you CAN get a query to do what you need: First, you should write a
second query, based on the first one, to calculate the Grand Total. After
that, you can perform a UNION query just to show all results together. [BTW,
that will be a non updatable query].
If you want a detailed SQL solution, then It would be better if you post
your original query.
Tonín