There is nothing more annoying than your tool making changes behind your backs.
Just make sure that everyone uses exactly the same settings. When you think that's done let developer A take a file, copy all, delete everything, paste. That will usually reapply all the formatting that your IDE wants to apply. It will change your file.
With the saved file, do the same again and pray that there are zero changes. Pass that file to each other developer in turn, let everyone do the same thing, and make sure everyone has their IDE set up identical this way.
If someone has an IDE that cannot be made to play nice, disallow its use. And now where everyone is in the same place, check out every single file, copy/delete/paste, check everything in and you are done.