I imagine that the original poster want the Nth salary, ie the one with N - 1 salaries higher than it, whether they be distinct or not.
This one is a little more compact, and I think it may perform better if your table is large. I have used the roysched table from the pubs database as an example; please adapt to suit your needs.
SELECT TOP 1 royalty
FROM (SELECT TOP 5 royalty FROM roysched ORDER BY royalty) x
ORDER BY royalty DESC
John