As I've mentioned before, at the Zen Centre, "incense offering" is a polite way of saying "monetary donation" sometimes; if you're taking part in a ceremony that's benefitting you directly -- for instance, becoming a formal student of Sensei or, in this case, taking jukai -- you make a donation to the centre in generosity and gratitude. Personally I wish they'd call it dana and not "incense offering", but I had to laugh when I read this in the email sent to all members with info about this weekend's jukai ceremony:
What amount constitutes a proper donation is up to each individual. However, it is not appropriate to place an envelope that is empty or that contains a few cents in the offering bowl. Offerings such as sticks of incense or flower petals are also inappropriate.
There's some history in that paragraph, I'm sure!