If you want to be pedantic about acceptable variations choosing something with such a long history and such wide use in various disciplines is a terrible plan.
"Percent" is probably the most common flavor currently; but 'per cent', 'per cent.', 'pct', 'pc', and likely others are still within the realm of accepted use. Hell, the '%' sign isn't even entirely settled, unicode has something like four defined variants. And that doesn't count the archaic, but historically used and still recognizable, specimens that cropped up between Latin and the present day.
I take it that you were exposed to basic literacy and only basic literacy, none of that messy intermediate stuff.