I would say the last s is more of an sh sound, but as T42 says, there is unique Portuguese way that - as far as I can hear - is actually pronouncing each letter, but in such a manner that it sound like a dipthong. Almost.
Kah-s-kah-ih-sh is how I would do it. (ETA elided without the pauses indicated by the dashes)
Eg, Coimbra, the nearest big town to where my shit-for-brains BiL&SiL have retired to. They think it is supposed to be pronounced Queem-brough, which actually isn't a bad approximation of what it should sound like: Koh-eem-bra said so it almost sounds like, well, queembrough