Is there a way or website to find the tenure and tenure denial rates by universities and departments? I heard from some faculty that the tenure rate at X university is Y%, so I wonder if there is a way to find the statistics for all universities.
No. Most institutions would consider tenure denial to be a confidential personnel matter. This information probably cannot even be obtained using freedom of information laws.
A small portion of institutions have their newly tenured faculty announced in Inside Higher Ed.
You can estimate faculty retention rates by viewing archive.org's records of the list of faculty on the university website. In practice, tenure rates are not as important as retention rates. There's no point in getting tenure at an institution you don't want to work at.