ta chemise est blanche et jolie.
nouns are masculine or feminine in French. Chemise is feminine (une chemise), so all adjectives attached to "chemise" have to be feminine.
ton chemisier est blanc et joli (your blouse is white and nice) - un chemisier, masculine, all adjectives masculine as well.
The translation to and from "joli(e)" and "beau/belle" is a bit difficult, for it changes on the object:
Men are not described as "joli(s)" (pretty) but as "beau(x)".
- joli(e)(s) = pretty/lovely (people) + nice, cute (things)
- beau, belle, beaux, belles = beautiful