I just made the list above based on my experience. I do 19 miles each way every day in NJ for one and half years now. For a 5 mile commute, you will eventually need the bike stuff, but it will take you four times as long before you have to worry about it. I started with an older bike and wore out a lot of stuff.

There are also items you need to commute that didn't make my list because I already had them - my pump, lock, portable tire pump, basic tools, and backpack come to mind.

I also forgot some random, miscellaneous stuff from the list - a cable cutter, cable ends, brake pads, and a caliper.

I also installed aero bars on my circa 1990 mountain bike, but they were free.

​​​​​​Winter related needs will also obviously vary.