Technically there is no legit method to root since rooting is itself unofficial .
How exploit based rooting methods work .
An Exploit opens up insecure shell on your device.(Also known as temporary shell root,temp root ,adb #...)
You push the su binary and superuser.apk (or SuperSU/su ,)and probably busybox via the temp. insecure shell and make the root permanent .
Exploits may vary/work device wide to manufacturer wide to Android wide (zergrush and ratc)
/About non root cache cleaner
I have heard some good stuff about
ES Task Manager
Also sammyz is an ork not troll .