There are many factors affected by temperature including, but not limited to, dissolved oxygen, toxic concentration of ammonia and nitrite, biological activity like rate nitrification, growth rate of fish, growth rate of plants, etc.

@David depends on your instrument, a digital thermometer would simply display decimal points, but anything graduated may have a difference given the ease of reading the number, i see your point though, but I convert it all in my head anyway so makes no difference to me