90 cents? Ask first if the seller even has a valid HST account number.
If so, then he does have the authority to collect it. Whether he remits
it to CRA is CRA's problem, not yours.
I used to BIN for many photographic accessories but the shipping has
noticeably slowed down and I've had to make more claims. However, in a
few case I have been provided with a tracking number and they show the
item was dispatched shortly after remit...