Many of us have products/plans/services that are in whole numbers so when you show it on the checkout page, it will show .00 after the whole number.
So if you are selling $99, then it will show up as $99.00 and this does not look esthetically pleasing. Psychologically it's been shown that this is not a good number to show and it should be kept a round number without decimals.
Please vote on this if you feel that MemberMouse should add a feature which will remove the decimals whenever it is .00. Of course, the decimals would show if it's anything other than a whole number.