What makes a sound "8-bit"
Old game hardware had only a few simple voices: square and triangle waves, plus a noise channel. Pitch slides, quick arpeggios and short envelopes did all the work. These sounds follow the same recipe, so the coin is two square-wave notes, the jump is a rising slide and the explosion is stepped noise sweeping from bright to dark.
Two original jingles
The level-up and game-over tunes are short melodies written for this site, not borrowed from any game. They are about one and two seconds long, which is enough to mark a stage change without getting in the way.
Using them in a project
Download the MP3 and drop it into your engine, editor or slide deck. Because the sounds are CC0 you do not need to credit this site, and you may edit them (trim, pitch-shift, layer) freely. Short sounds like the coin and jump work well played repeatedly on a hotkey.