Coin conservation failure

I was at the supermarket a while back, buying groceries.

The clerk tallies everything and says: "That will be 2,451 yen, please."

So I pull out my change purse, and seeing that I have an inordanate number of little, irritating, completely useless, aluminum 1 yen pieces, I decide to give her 2,506 yen; 2 1,000 yen notes, a 500 yen coin and six of those damndable aluminum coins... Seems reasonable, I give her six little aluminum coins, she gives me 1 copper coin. At least you can give the 5 yen pieces to the temples (They have a hole in the middle, making them lucky... That takes some explaining, just take my word for it, giving them 1 yen pieces is bad form)...

Now, my plan is brilliant; she will give me a 50 yen piece and a 5 yen piece. I will have traded 7 coins for 2... I will have saved room in my already bulging coin purse that randomly leaks 1 yen pieces into my backpack or pocket as it fails to maintain structural integrity due to an overload of aluminum...

What does she do? She smiles, mumbles an apology in super-polite Japanese, slides the 500 yen piece into the change sorter and gives me back my 6 yen... with that "Yeah, you probably don't really understand how to use that "money thing", do you?" look on her face.

And then promptly gives me 49 yen in change; 4 ten yen pieces, a 5 yen piece and 4 MORE stupid, little, aluminum 1 yen pieces.

So... I gave her one coin and gained 9 coins...

I tried to argue, by my Japanese-speaking brain is slow to react and I am thus greeted with the pleasant Boop Boop Boop sounds of her checking the next customer in line...

As I fed the last of my newly aquired gains into my strained coin pouch, it just looked back at me with that, stupid, metallic, overwide grin...

And then, just to spite me, it spat a couple of those 1 yen coins into my pocket...