Grouping can be done by dates (the date of the relevant commit):
i suggest showing the last 3 tags in the list, and then start grouping like: last week, last month, last quarter, last year...
you can allow for configuration of the time periods, or just allow grouping by time.
Grouping can also be done by name - then you will probably need to allow configuration of seperators, or regex that split the tag names into groups.
This way tags of the same thing can be grouped together based on the split.