Safari wants to access my keychain doesn't offer "always deny"... How can I implement this? The only choice Safari asks me w.r.t keychain access is "deny" or "allow" or "always allow".

Why doesn't Safari offer me an "always deny" option in Safari?  How can I make the system "always deny"?

Will the "always allow" or always deny apply to the computer or to a specific website?
There is not an always deny functionality in keychain. Put another way, there is a white list but not a black list. 

A somewhat elegant workaround is to turn off AutoFill of passwords in Safari's preferences and you won't even get the request to access the keychain in the first place.