Earlier, when I talked about temperatures, I rather had in mind the impact on the mechanics involved, but you are right: the temperature has an impact on the volume of any liquid, including gasoline. In Canada, the great majority of gas pumps are corrected to 15 degrees, which means that the variation in temperature is taken into account. Therefore, as far as measurement is concerned, no matter what the temperature, consumers will always get a fair measurement.
On June 3rd, 2010. See this statement in context.