by blocking the door. It isn't recommended because when you open up, all your inventory gets sold super quick to make up for the time the shop was closed.

It is better to block the cash register.

As long as your happiness remains at 100% what does it matter? Are you not selling anything? If your happiness is 100% then you are selling stuff...besides this is a bit more realistic because NO STORE out there sells something to every single one of the customers that come through the door.

IF you exit the game stuff sells a bit quicker than if you sit there and watch it.