Written - spoken finnish
Do you say Kymmentä in the written language and kympiä in the spoken language?

Question

Answer

Yes, but it's "kymppiä" :)  and normally you only use it when you talk about money (kymmentä euroa --> kymppiä)
otherwise you say "kymmentä" also in spoken language (kymmentä autoa --> kymmentä autoo)

I hope this helped somehow .__.

Answer

I am not a native finnish speaker but, I have made a research and the answer is yes.