Hi VirginBlue Kris,
You should try using
CACHE::uri, or more specifically CACHE::uri [HTTP::path]. This should cache and return the base path (minus the [HTTP::query]), thereby removing the uniqueness.
See the CACHE::uri for more information, but this quote from the page may explain some of what you are seeing:
Cached content by default is stored with a unique key referring to both the URI of the resource to be cached and the User-Agent for which it was formatted. If multiple variations of the same content must be cached under specific conditions (different client), you can use this command to create a unique key, thus creating cached content specific to that condition. This can be used to prevent one user or group's cached data from being served to different users/groups.
Hope this helps.