We probably need some more details to be able to help - maybe you can create a workbook using the Superstore data & blend with data mocked up in Excel?
That said, I've solved some thorny fiscal year issues by not using the built-in fiscal year functionality in Tableau, but rather creating an "Adjusted" date calculated field that simply translates a FY date into a CY date.
For example, if your fiscal year starts in April 2015, you can "adjust" all dates to calendar 2016 with the calculated field:
DATEADD('month', 9, [My Date])
So April = January, May = February, June = March, etc.
Maybe this will spark an idea for you...
Otherwise please post a packaged workbook & I'm sure someone here will help you out.