Any time you see the world “slots” preceded by a money amount, you are just learned something important. A penny slot is any machine that sets the value of one credit as one cent. This phrase does not mean that every spin of the reels will cost $0.01, just that each credit will set you back a penny. Casinos organize their slots, quarter slots, half-dollar slots, and dollar slots. Penny slots are generally the least-volatile games on the floor. That means these games take less of your money over time than their more-expensive cousins.