So the FM center frequencies are determined as follows:
88.0 MHz + 0.1 MHz = 88.1 MHz 88.2 MHz + 0.1 MHz = 88.3 MHz 88.4 MHz + 0.1 MHz = 88.5 MHz
107.8 MHz + 0.1 MHz = 107.9 MHz
Every FM center frequency ends with a decimal extension of .1, .3, .5, .7, or .9.
In the AM band, each AM station has a maximum bandwidth of 10 kHz, extending 5 kHz above and 5 kHz below the assigned center frequency. The AM band in the United States covers frequencies from 540 kHz up to 1700 kHz, in 10 kHz steps (540, 550, 560 ... 1680, 1690, 1700). 530 kHz in the United States is not available for broadcast use, but is reserved for the use of very low powered Travelers' Information Stations. AM band stations do not have assigned channel numbers, they are referenced by the frequency in kilohertz only.
AM and FM station assignments in other countries may not be made according these procedures. In some countries, an FM station may be assigned a frequency with an even decimal such as 106.2 MHz. In many places, AM broadcast stations are assigned on frequencies with a 9 kHz bandwidth (531 kHz, 540 kHz, 549 kHz, etc.). There are a few AM stations assigned in the United States in this manner, in Guam, the Marianas Islands, and American Samoa.
Updated: February 4, 2014
Additional information about AM and FM broadcast radio stations is available at the Audio Division on the FCC's website.