With a trigger lock on, or a cable lock through the action, you can just leave the darn thing lying around anywhere in the house if you want. The only stipulation you need to worry yourself with, in uncased storing or displaying of non-restricted firearms is that the ammo cannot be readily accessible to the firearm. Essentially your four options are:
Guns and ammo in the same room:
1. Gun is locked in a "difficult to break into" case, no trigger/cable lock required. Firearm is not openly stored/displayed, so it considered not within easy access to unlocked ammunition.
2. OR the ammo is locked in a box/case, gun can be out of case, also with secure locking device in the trigger/action.
3. OR gun AND ammo are both are locked in the same "difficult to break into" case, no trigger/cable lock required. Neither are considered legally within easy access to each other when they're locked together.
4. OR the uncased gun, and unlocked ammunition, are located in very different rooms from each other, with just a locking device on the firearm trigger/action.
Ammunition should be responsibly locked up anyway, whether its in a safe, cabinet, or hardcase with the firearm. The "Careless storage of ammunition" offence in the Criminal Code is very subjective.
86. (1) Every person commits an offence who, without lawful excuse, uses, carries, handles, ships, transports or stores a firearm, a prohibited weapon, a restricted weapon, a prohibited device or any ammunition or prohibited ammunition in a careless manner or without reasonable precautions for the safety of other persons.
It doesn't say to specifically lock it, but if an officer can determine that it's somehow careless, you're gonna get nailed. You can also be charged under the Explosives Act for careless ammunition storage as well.
Save yourself the potential grief and put a cheap lock on your ammo box(es). That way as long as you follow the RCMP storage pamphlet, ammunition is not going to bite you if your gun isn't in a case at any point.