I'm in agreement with other answers. Birth years are most often estimations made by the enumerator. What is odd in this case is that James King is born in Pennsylvania, Iowa and New York. Is his address different in each census? Is the family composition different in each census? Do you find some of the same family members from one census to the next? Who is Michael McGuire in relationship to James?
1870 - Winona, Elba, Minnesota. James King, 22, born in Pennsylvania in household of Michael McGuire; others in same household: Sarah King, 24, b in Ireland; Etta King, 1, b in Minnesota; Ellen King, 0, b in Minnesota; Patrick King, 34, b in Ireland. (Note: Estimated year of birth 1848. Also there are more than a dozen other James Kings in Minnesota census in 1870...)
1875 - Winona, Elba, Minnesota. James King, 26, born in Pennsylvania in household of Frank and Mary Rodmaker. No image available. (Note: Estimated birth year 1849. These two James King's look like the same one, given age and birth place. Was he a boarder? Don't know)
1880 - Winona, Elba, Minnesota. James King, 30, born in Pennsylvania, head of household, married to Amelia, 28, born in Germany. James has 3 children born in Minnesota : George age 4; Charles age 2; Unnamed King age 0. He has one stepson, presumable Amelia's child: Louis Bohn.
These three James King's appear to be the same person. The estimated birth years do vary frequently. But the birth place in my experience is more often exact, and that's the case here. Also, the sequence is coherent. Single in 1875, father of three in 1880. All in the same town :)
Now the question is, is this the person you're interested in or was it another James King you were looking for?