On a related note I have always pronounced the musical interval “cent” (1/100 of an equal-tempered half step) as [sEnt], but had a piano tuner a year or so ago who kept pronouncing it as if in French, which I’d never heard.
Nearly all men and women who had an undergraduate education in the US had to take physics, chemistry, and biology. There they learned the proper English pronunciation of “centimeter.”
The English pronunciation of “centimeter” (“centimetre,” British spelling), and the French pronunciation and spelling of “centimètre” are all acceptable. I doubt, however, that English speaking physicians and other medical personnel use the French spelling. The French pronunciation by English speaking medical personnel may be an arrogant and/or peer pressure pronunciation which tells the uninitiated that the speaker is special because he/she works in the medical field.
I’m sorry I needed to repost/correct the former message because of further important points.
Nearly all men and women who had an undergraduate education in the US had to take physics, chemistry, and biology. There they learned the proper English pronunciation of “centimeter.”
The English pronunciation of “centimeter” (“centimetre,” British spelling), and the French pronunciation and spelling of “centimètre” are all acceptable. I doubt, however, that English speaking physicians and other medical personnel use the French spelling. Furthermore, I do not hear American medical personnel use the proper French pronunciation of “centimètre,”which, phonetically written by Quartz above, is “son-ti-mett-ruh.” Note the “mett-ruh," which one doesn’t hear. The imperfect French pronunciation by English speaking medical personnel of “centimeter”may be an arrogant and/or peer pressure pronunciation which tells the uninitiated that the speaker is special because he/she works in the medical field.
Looking for creditability for the mispronunciation of this French word by referring to the French Republic’s 1799 introduction of the metric system, or to the modern form of the metric system, the International System of Units (French: Système international d’unités, SI units), seems far-fetched.
Aaren Aarnensen, welcome to the Straight Dope. Please note that this is an old thread, so some of the earlier posters may not be around any longer.
Regarding your last paragraph–if you stay here, you will find that no nit is too small to go unpicked, and the far-fetched is a way of life around here.
Some are 6 sontometers underground.
More than that I hope - at least a fathom.
More like a centifurlong I reckon. 
Were students ever graded on whether they used the “correct” pronunciation, or was this more of a tradition/school colors type thing?
I only have a vague memory of this thread from four and a half years ago and no memory of the early thread I was referring to there.
This thread isn’t going much faster than a few centifurlongs per microfortnight - and you have to put an “eee” into “micro” nowadays, like they do in Spanish.