Ayn Rand was not a conservative, and Objectivism is not a conservative philosophy.
The primary thing Ayn Rand and conservatives have in common is that they each advocate less government interference with and redistribution of private property than those on the left do. Rand is called conservative because economics is the first dimension that political beliefs are typically categorized with, and because Republicans are more likely to cite her as an influence than Democrats. But the difference between Ayn Rand's philosophy and the conservative movement - now and earlier - is massive. Ayn Rand was a critic of conservatism just as she was of the left.
Naturally this post overlaps with the one on Paul Ryan, but to reiterate somewhat, there are numerous differences between Ayn Rand's beliefs and conservative ones. Foremost, Ayn Rand was an atheist and strongly supported the right of women to get an abortion. But while the fact that Ayn Rand was not a "social conservative" is relatively well-known, her economic and foreign policy differences with conservatives are often ignored or understated.
The difference between Ayn Rand's views on foreign polciy and that of conservatives, or at least today's conservatives, are considerable. Contrary to the self-sacrificial nation-building and "spreading democracy" advocated by Neo-Cons, Ayn Rand believed that the sole and absolutely vital purpose of the United States military is to protect the American people, and that military engagements should be executed with only that standard in mind. This made the combination of positions Ayn Rand and Objectivists take on foreign policy decisions appear incongruous to those who think in terms of "doves" v. "hawks." Rand was, for instance, an early opponent of the Vietnam war, yet criticized the Carter administration for not reacting to the Iranian Hostage Crisis with immediate military force.
Most underplayed is how much conservatives differed from Ayn Rand's economic views. Contrary to what left-wing pundits say about the Republican Party, they are not "Randian radicals." Rand was far, far more radical. Objectivism upholds "the complete separation of economics and state," and a government limited to the police, the courts, and the military, existing for the sole purpose of protecting citizens against the initiation of force, theft, or fraud. While the Democrats critique Paul Ryan for wanting to turn Medicare into a voucher system in order to slow down the increase in spending on it, Objectivist intellectuals are advocating the phasing out of Medicare, Medicade, and Social Security alike, not to mention various other redistributive federal and state programs. Rand criticized conservatives on other economic issues as well, calling Reagan among other things "an advocate of a mixed economy with government controls slanted in favor of business rather than labor (which, philosophically, is as untenable a position as one could choose)." Today's Republicans are considerably closer to the Democrats on economic issues than they are to Objectivism.
All of these differences are rooted in the fact that Ayn Rand's philosophy is fundamentally contrary to both today's left and today's right, and the cultural philosophy they both exist in, that has made those the two options. Ayn Rand challenged the basic moral and epistemological philosophy that has existed up to this point, and her political views are an application of that, inconceivable without it. Conservatives do not represent a political philosophy at all, but by definition want to conserve the status quo. Ayn Rand was one of history's greatest challengers of the it, institutionally and philosophically.