Technically this translates to "(from) Monday to Friday". There are ways in French to specify "through Friday". Sitesurf posted one, and if I come across it again, I'll provide the link.
Beyond that, in spite of its widespread North American usage, "through Friday" is, in my opinion, an absurd hypercorrection. Generally we don't wonder if "(from) Monday to Friday" includes Monday, and it should be likewise with Friday. It's included unless otherwise specified. (Everyone knows this. Why the anxious substitution of prepositions?)
And in French it's the same. "De lundi à vendredi" includes "vendredi", but there are ways to make extra extra sure.
Just be aware that 'til is a questionable spelling. See the usage note here:
Till and until are both old in the language and are interchangeable as both prepositions and conjunctions: It rained till (or until ) nearly midnight. The savannah remained brown and lifeless until (or till ) the rains began. Till is not a shortened form of until and is not spelled 'till. 'Til is usually considered a spelling error, though widely used in advertising: Open 'til ten.