I did a quick search for this put didn't find anything.
Some errors slide off the top of the page, which make them quite useless. I was picking out shops in the magic buy thing (cool feature BTW) but after I attempted to "add to carts" a series of errors appeared at the top of the page stating that various parts had to be added in batches of 10. I'm cool with that, no problem adding a part here or there. But the errors disappeared a couple seconds later so I had no way of keeping track of what needed to be changed.
Comments
Even if I do round out to the nearest 10 (or what ever the store requires) there would be no point since the magic thing might decide to buy out all of Sitex's parts and then allot the remaining to SiteY.
To illustrate my point, assume I need 18 of a part, but I up my minimum to 20 and only two sites have the part:
SiteX has 16 of them at $0.04, no restrictions
SiteY has 100 of them at $0.25, but requires you buy in batches of 10.
The magic thing will place 16 in the cart for SiteX, but I'll get an error for trying to order 4 from SiteY every time.
What it should do is order 10 from SiteY, and then 10 from SiteX.
And since the errors disappear so quickly there seems to be nothing I can do to balance out my orders.
It doesn't work in the example you have given though, it would allocate 16 to SiteX as they are cheapest, it would then attempt to allocate 4 to SiteY, but it would not do it as it won't meet the batch requirement. For it to work on that scenario it would need to do a brute force kind of approach where it works out the absolute best way to purchase the items which is a bit tricky at the moment.
If there was a SiteZ that was more expensive than the SiteX but had no batch requirements it would allocate then there.