This is in fact possible via Local Storage. And you don't need to clear the cache, you can just detach the last save file or overwrite it if possible but you cannot delete the save file or clear the cache using html5.
First in your game update project add the "LocalStorage" plugin and add the key named "Version".
Then add this event.
*On start of layout
------> Local Storage.Get key ("Version")
\\*Let's say that the new game update version is "1". If the key "Version" is only available in the update, the key "Version" will be 0 in default**On Item get ("Version")
*If LocalStorage.Item Value < 1
----------> (Detach the save file of connection with your game until it is overwritten by a new one. I don't know how you made your game so it is up to you.)
----------> LocalStorage.Clear
---------> LocalStorage.Set Item value to "1"