Using ROUNDUP and a Minimum value (that doesn't round) in the same function.

So I'm making a pricing sheet for my boss, and I've run into an issue. The situation is basically we have a $15 minimum on something, and we charge $20 per 1000 of a product. So if it's under 1000, we charge 15. But for over 1000, it needs to round up to the nearest $20. (so a job of 1500 would charge the same as a job of 2000) (it's a setup fee, sort of.)
And I ALSO need the function to recognize a Y/N field.
I got everything to work, but it seems to be rounding my $15 up to 20, which I don't want it to.
This is my formula thus far:

=IF(C18="Y",MAX(15,ROUNDUP(PRODUCT(H6,0.02)/20,0)*20),0)

So C18 is my Y/N field to mark if we're adding the charge
and H6 is my qty that we're doing. the 0 at the end makes that field 0 out if we select N for the charge.

Thanks in advance for the help!

EDIT: Just realized I think I posted this in the wrong category. And I can't delete this to repost it. Can it be moved? I'm SORRY.