With latest tableau version, you are able to do a Geo join with shp file and data file as shown below
the reason using round is the full decimal is not easy to match each other as the dots are just a bit of difference.
and the result is like this for the overlap ones.
I attached the workbook for your reference with 2018.1 version.
Hope this helps
Book1_v18.1.twbx 4.3 MB