I have some decimals in the distance of every single pokemon I have walked. Not only that: I have probably lost 10 candy adding all the remaining distance of all of them. And my life hasn’t got any worse at all since I did it.
You shouldn’t worry by that. I used to be like you, but I learned in the bad way being so perfectionist won’t bring anything good. You should learn to not care so much about it and simply, let it go.
However, if there is something deeper and you really, really, but REALLY can’t do nothing about it and the stress level this causes you is so big you can’t deal with it, fortunately, a solution exists. In fact, it is very simple: walk 4’9 km more. Or more, because you will need Bagon candy in the long term.
Please, make me a favour. DON’T DELETE THAT SALAMENCE UNDER ANY CIRCUMSTANCE!!! Seriously, Salamence is really good, don’t quit him because he has 0’1 distance walked.