Open the package of straws. Spill the straws out of the package onto a large open surface, such as a tabletop or the floor.
Count out 10 of the straws. Place that group of 10 in a pile separated from the still-uncounted straws. Repeat nine more times, until all 100 of the straws are in piles of 10.
Pick up one of the 10-straw piles. Holding the group of straws in a vertical position and in a loose grip in one hand, tap it against the tabletop or the floor so that all of the straws are aligned.
Twist a rubber band over one end of the group of straws, about 1 inch from the end. Twist a rubber band over the other end of the group of straws, roughly 1 inch from the opposite end.
Repeat tapping each group of straws so that they're aligned, and binding them into a bundle by twisting a rubber band near each end of the straws, until you have 10 bundles of 10 straws each.