If it's selfish voting to benefit myself then why aren't minority groups just as selfish for voting for themselves ?

voting isn't selfish. your whole notion makes no sense. BTW, NOT voting is selfish.

If selfish, it's appropriately selfish. There is a time for everyone to be selfish. And in this instance, being selfish isn't actually selfish because one voter voting doesn't actually realize their self-interest but serves their country by revealing to their country what the national interests are, what its sovereign citizens collectively say constitutes America's self-interest.

So anyone and everyone should vote in accordance to their self-interest. That is because it's not any one vote that elects someone to office but is the aggregate of all votes that does. So by voters voting in accordance to their self-interest, the aggregate of all voters' votes in accordance to each's self-interest becomes an expression of the self-interest of America, an expression of what is in America's own self-interest. 

That's the point of American democracy, for the body of voters to express their self-interest because their collective self-interest is America's self-interest, what interests America is charged and mandated by its sovereign citizens to serve. If voters fail to vote in their self-interest, America has a government that neither knows the self-interests of America nor serves them but some other interests, interests that are not America's own. Like when America goes to war, it is, among other things, to protect American interests, America's self-interest, which in America where the government is by the people and for the people, America's self-interest is determined by voters voting and those votes coming together in aggregate to express the self-interests of its sovereign citizens. 

This does not contradict the ideas of service to ones country or "ask not what your country can do for you but what you can do for your country" but quite to the contrary. That's because by voting, I am doing for my country, and by voting in my self-interest, like everyone else is charged to do, I am actively practicing good citizenship by being part of the democratic process that reveals what is best for this country and thus engaging in doing what is best for this country. 

Voting in one's self-interest being in the interest of everyone is not just a tenet that must be followed for America's government to properly function, but it is also a tenet that must be followed for its economy to properly function. The backbone of America's free-market economy, as explained by Adam Smith in The Wealth of Nations, is that everyone in the economy vote in accordance to their self-interest, the "votes" in the American economy being cast by consumers with dollars they spend. Were enough Americans to stop acting in their self-interest economically, the economy would breakdown because the "invisible hand" that guides it is the result of the aggregate of self-interest being aggregated through the expression of self-interest by individual consumers casting votes in accordance with their individual self-interest with dollars they spend.   

i dont vote for my benefit at all...yes you are selfish.  i want the people who have less...to have less taxes and less burden