If this has somehow been implemented then just ignore.
In my opinion it would be useful to be able to add certain coins to keep list.
For example if you're carrying mithril around that you don't wish to part
with,
you could add mithril coins, or even a certain amount of them, to keep list.
Now when buying something from a shop these coins would be ignored.
The prerequisite of course is, that there are other idiots like me who forget
what they're carrying:)