If you've ever been to Sweden, you may have noticed we're a country with a coin deficit. As of October 2010, the coin with the smallest denomination in Sweden is 1 krona (approximately 10 Euro-cent or 12 USD-cent). One krona is equal to 100 öre but there are no valid coins which you can use to pay a fraction of a krona any more.
But the öre is obviously still in place: you can see it on your bank statement, when you pay in the store, and so on. However, as it's not possible to pay any öre with cash, there's a lot of cash rounding going on. Interestingly, at least for the local supermarket I frequent, their systems apply a different logic depending on if you pay by cash or card.
If you pay by card, the system charges you exactly by the öre what you owe to the store. So if that's 14.58 kronor, you pay exactly 14.58 kronor. If you decide to pay by cash, they round it up so you need to pay 15 kronor instead. Had the sum total been 14.48 kronor, they would have rounded it down to 14 kronor.
So the obvious question seems to be: how much would you save if you gamed the system such that you always paid in cash when the rounding was in your favor, and by card, when it was not? Assuming an equal distribution between the two occasions, you would expect to be able to save on average about 25 öre per second transaction.
If you frequent the store on a daily basis, you'd save a whopping total of 3 krona 75 öre. Enough to buy yourself.. half a stamp. Okay, moving on. Let's see what this looks like in practice. I tend to always pay by card, so I retrieved my account statement for the previous two months.
Turns out out of the 170 transactions, there are only 23 where this would work in my favor (meaning they have en öre portion of less than 50 öre), but it would have saved me 5 krona 88 öre. Enough to buy two packs of noodles. Yum!