How to juggle 5 balls
To be able to juggle the 5 ball cascade is a big milestone for many jugglers and comes with lots of practice and picking up balls off the ground.
The first exercise you want to try is the 552 siteswap. Similar to the five ball cascade, but performed with four balls. Tosses are made consecutively from the same hand, being a relatively slow-paced pattern while you still throw roughly the same height and angle as the five ball cascade. This pattern is a good exercise for making your throws more accurate. See animation.
The next exercise is the 5551 siteswap. Throws are performed the same as in the 552 except you add a straight horizontal pass between your hands. This heightens the pass and will prepare you for the fast pass of five balls. See animation.
Once you have the 5551 down, you can try this final exercise. The 55550 is essentially a four ball pattern juggled as if it were a 5 ball cascade, but with the fifth throw left out. Where you would throw the fifth ball in a 5 ball cascade, you simply do a pause instead. The 55550 will teach you to time your throws properly. Pay attention to the pause and try to get it consistent. When your timing gets sloppy, the pause will be inconsistent and mess up your pattern. See animation.
Adding the 5th ball
To add the fifth ball I recommend you practice previous steps thoroughly. Start with three balls in one hand and two balls in the other. Make an arched throw from your dominant hand(holding 3 balls), and follow it up with two more tosses at the same height, alternating hands each toss. Three balls are now in the air and you have one ball in each hand. The ball you started out with is now falling towards your non-dominant hand, throw the remaining ball that's in your hand to make room for the catch. Same thing is now happening with your dominant hand, throw your last remaining ball to make room for the second catch. The next challenge you face will be actually catching all 5 balls, practice flashing first and focus on your throwing angle and catching. Keep adding more throws as you get more comfortable. Can you do a flash? Congratulations! You are now part of an elite group of 5 ball jugglers, to which only an estimated 0.005% of the world population belongs to.