Barclays Launchpad are testing this!
Rounds up to nearest 10p and you can set a max monthly limit. They have a list of registered charity’s you can choose from (which will probably grow over time).
I’d attach screen shots but the apps ‘security policy’ wouldnt let me take any.
This wouldnt have to take masses of time from Monzos developers, dont Monzo set aside ‘Monzo Time’ for developers to pursue their own projects? Some of them could consider doing this as a side project.