Display price for single products but only allow purchases in multiples of 6

HI

I have a client who needs to be able to add products to the system e.g. Cup for 0.99 but requires a restriction that the purchaser can only buy in multiples of 6
i.e. the purchaser sees the item priced individually but when its added to the cart it is added with a quantity of 6
The restriction must flow throughout the system, i.e. the purchaser cannot update the quantity in the cart to something that is not a multiple of 6

Is there any functionality in nopcommerce that can achieve this?

See this contribution (not available in official releases). Also have a look at this changeset bc003545550a (will be available in the upcoming version 2.60)