I believe to keep things simple and easier to understand they’re rounding to whole numbers when in actual fact, when it comes to investing, it will be a slightly different amount. For example, someone asked this:
and someone from Monzo answered this:
Then someone asked this:
and were told by someone at Monzo this:
Which again I think is simplified to mean 1 share at £7.71
This is backed up by the code found in this topic: