Take the stylus and shake trees that are in the area around Taj's Tent. (Take your stylus and tap the trunk of the tree. You should here a creaking sound. One you here the creaking sound, move the stylus back and forth quickly. If you do it right you should hear a sound and the coin wil appear on the ground near the tree, and on the map. This cheat can be used infinite times! Once you shake all the trees in the area go away and come back and you will be able to do it again.

Or

Go to the coast near the water fall that is under the log tunnel. After you get there, you should see little dots in the sand. (This area is to the left of the water level's entrance) When you are approaching it, you should also see a hand icon like you do at the cracked wall where you find the discover card. Tap the hand and you will have an overhead view of the sand. You will notice two round shapes formed by the dots. One in the inner part, and one on the outer part. Connect the inner dots as best as you can be making a small circle from connecting them. After you are done, push the back button (top right). If you did it right, you should hear the same sound as you do when shaking the trees. After you hear the sound, there will appear about ten coins. This cheat can be used multiple times, but not infinitely.