Since you want totals at the yearly aggregation and your date dimensions are organized by Month > Year, you need to go outside the default functionality, which will only give you subtotals at the month or grand totals at the month+year level. I'm sure you knew this already, just repeating to clarify for myself.
There are a couple of approaches. The first and easiest is to just duplicate the worksheet, remove month from the columns shelf on the second sheet. This should give you your yearly totals. Now you can combine these two sheets in a dashboard. The main problem with this is that you can't select or expand hierarchies (you can do it on the main sheet, but it won't be reflected in the second sheet).
The other approach is to use custom SQL to duplicate the data set with a UNION ALL, adding a "source" identifier on each row to indicate data or totals. This enables you to create a custom month calc that for "data" rows returns the month and for "total" rows, returns "total"---both are then partitioned by year on the columns shelf.
The attached workbook has examples of both and more detailed instructions.
You should also check out Jonathan Drummey's excellent presentation here on totals and sub-totals: TDT: Grand Totals & Subtotals with Jonathan Drummey - May 9th @ 9AM PT.
totals.twbx.zip 1.6 MB
this will work great for me, thanks much.