Theoretically, anything can be done in the RMs. The entire engine is open source and anything can be changed in the javascript.
However, the engine is not geared toward a shop simulation, so you'll have to enter a lot of changes and plugins into that to make it into such a game.
That can be done (in fact there was a tavern-simulator based on RMXP on steam until it had to be taken down because its team split up in a bad way with legal problems), but it is a lot of work.
If you can program yourself and have no fear of that work, go on - for a small game on the side you'll better look for an engine that is targeted on simulations.