What pattern is it? Where do you cast on, at the beg or end of a row?
If it's at the edge, you can use a knitted or cable cast on, using the edge st in place of the slip knot. I'd CO 5 sts at the beg of 4 rows to get you 10 on each side' that way they're more gradual.
But if it another type of top, we need more information.