In my opinion, your manager is absolutely right. Buying a car is already an unpleasant, and to varying degrees stressful, experience. For some reason, for me, a salesman's scent always makes him seem slippier, even if I would have enjoyed it in any other setting -- nearly any scent decreases my confidence in him. If I had to smell something on my salesman, it would have to be one of those scents that isn't particularly well-loved here, like fresh-smelling aquatics, soapy clean scents, applied so that there's zero sillage and I have to be very close to smell it at all
Honestly, pick something light and safe. When in business, you don't want your fragrance to make a strong statement. Let your product speak for itself.
So I'd say a light dose of Millesime Imperial, so basically everyone who is near you will think you smell good, but no one will be disgusted and you won't be that guy who wears too much cologne.
If you really want to challenge yourself I'd suggest 5-10 sprays of A*Men. If you've sold any cars by the end of the week you can pat yourself on the back.
In all seriousness light application of anything works best. I suggest Frapin L'Humaniste, Allure Edition Blanche, Dior Homme, GIT/SMW/MI.