You are in such a small organization that anyone in an IT-related position is going to have to wear many hats.
That said, you do need some boundaries & a prioritization queue. If your primary function is programming/software support, a random person from Corporate Accounts Payable shouldn't be able to come to your desk and stand over you demanding that the toner in the copier be refilled while you're trying to get a critical problem solved, or a new version of a piece of software rolled out to production.
What you need is someone to take these requests, get them logged, prioritized, and assigned to the right people. A deflector of sorts. And your manager must be made aware anytime these sorts of requests are taking enough time away from your other assignments that deadlines or quality are going to slip. If a person can't be appointed for this, perhaps a web-based ticketing system where people can submit their requests so that they aren't sent directly to your inbox, or people coming right to your desk interrupting you. Everyone in your group would then share responsibility for managing these requests.
In my company (about 3 dozen people in IT, 200 or so people total in this office), the IT department does not usually take care of toner & paper refills (our mailroom, who also take care of office supplies typically handle it), but if asked to they usually will.
Something like a broken microwave shouldn't fall on you "just because it gets plugged in" - in larger offices, that's handled by a maintenance or building services department. There should be a general office manager who handles calling the appropriate people (typically on service contracts) to make repairs - these folks often typically handle the weekly office supply orders that are fulfilled by Staples and the like. If an employee can't figure out how to operate a microwave oven and need instruction from the IT staff, perhaps that individual shouldn't be operating the device in the first place. If it's broken, it should be replaced or repaired - with that call coming from whoever is responsible for managing the upkeep of the building/space.