How do I stop the home button from waking my Samsung Galaxy S5?
If you rooted your S5 it is pretty simple (and you don't have to install third party apps): 
1) use a file manager and go into root -> system -> usr -> keylayout and find the file  gpio-keys.kl ;
2) Open it with a text editor and find the lines with "WAKE" written in them; 
3) Go to the one with "HOME" written in it and just delete this word and all the spaces between the number on the left and "WAKE" on the right;
4) Save the file and you're done;

If you can't do this 30seconds thing because your S5 is not rooted then I'd suggest you to root your phone: a new world opens right in front of you ;)