Similar entries with the greatest coincidence tags
Please correct me if I am making an incorrect assumption. From your example, it looks like you're passing multiple tags to the search query, and by greatest coincidence you mean that you want the Entries that have the most matching tags that are part of your search, to appear higher in the results than Entries that may just have a single matching tag.

I don't believe this is possible without an additional plugin that helps with modifying the scoring and order of the search results.