I was recently an Oval Money customer before my switch to Monzo and they utilised the roundup feature on purchases (but way less efficient, waiting a week for it to happen!).
However, they allowed for an additional dynamic roundup option to be ticked, where purchases over a certain amount (say £100) allowed you to optionally round up to the nearest tens of pound rather than the nearest pound.
Example: If I spend £141.50 on a coffee machine it would round up to £150, allocating the additional £8.50 to the savings pot, rather then just the 50p
Just a thought but a feature I’d welcome to Monzo’s app, keep the feature optional and let us set the trigger point, would be great!