Actually, you should be able to use camera raw 6.7 (plugin) in photoshop cs5, which should open those files into photoshop cs5.
Camera Raw plug-in | Supported cameras
Camera Raw-compatible Adobe applications
If in photoshop cs5 you go to Help>About Plug-In and click on the words Camera Raw, what version does it say?
If it's a version number lower than 6.7, you get the camera raw 6.7 update from here:
Adobe - Adobe Camera Raw and DNG Converter : For Windows : Camera Raw 6.7.1 Update
You can also try Help>Updates from within photoshop cs5, but that may not work.