LineChart values column doesn't show exact values

[aballano]

Hi there, thank you for the work in this lib, I've been using it for a bit and I noticed that the chart doesn't show the exact values for the points, at least with the ranges I'm using:

I created a LineChart with default params as an example with 2 points: Data0 - 5500 and Data1 - 6000

As you can see the leyend on the left shows a range between 5400 and 6100, which is fine, but then for some reason, the values are unrounded.

I'm not sure how's done at the moment, but it might need a bit of tweaking. I didn't have time to look into the source code, but if that would help please let me know where I can find the calculation for that so I might open a PR at some moment.