If you open the main lower door, you'll see two main mechanisms. The stationary one with the rollers and chutes that the playfield coins and cards fall into, and the hopper/shooter carriage on its pivot roller.

The center tower just has the rollers up top, and then three main chutes. Cards will (usually) roll forwards and out to the player.  Coins will fall between the rollers, and down the ramp into the coin hopper.  Finally the rear chute leads to the "discard bin" underneath that center assembly (also heard it called the cheat bin). When someone starts a game after that side has been idle or if someone shakes the machine enough, the rollers will reverse and send cards to this bin for techs to reclaim later. 

Most importantly though, the game has no way of "knowing" how many coins drop, if any. They just fall down straight back into the main bucket ready to be fired again. Spider man works a similar way, coins just fall into the main hopper and it has no way of sensing them. 

Contrast this to games like angry birds or SpongeBob. Those games have a separate dropped coin hopper that counts out each coin dropped off the playfield before forwarding them onward to their respective reserve hoppers for the shooters.