Bonjour Connie !
Thanks for this question that raises an interesting point, regarding the agreement of "cent" in French :)
Indeed, the rule is as follows: you agree "cents" unless it's followed by another numerical adjective (most numbers but "million" and "milliard").
I thought myself this rule applied to currencies, but I had it wrong, hence this mistake.
Thanks to you, it's nor been fixed in the test :)
Merci encore et bonne journée !