https://community.monzo.com/t/number-rounding/1069
You are not losing any penny. The correct amount would be deducted from all your transactions. 
Rounding off the figure makes sense, as this page is only meant to give you an idea for you spending. Being able to know that you spent 34p more on a category with a few hundred or less is not going to help you understand your spending more. This way, it’s much cleaner and easier to read. If you would like more detail, you can always tap on it. And if you need the total, you can use the Search to show you the exact total amount.