Values of capacitors
Look at a supplier catalogue for your resistors. They too are available in sizes of 2.7, 3.3, 6.8, 8.2 just like their capacitor cousins. Inductors follow this pattern as well. 

The sizes of components progress through the a series from 1-10 in a way that the neighbor values are within step sizes of 5%, 10% or 20%. You can read a nice write up in the concept of preferred values here. Look specifically for the E-series as it relates to electronics.