I noticed a couple of times already that I get send to a radio frequency that end with .43 or anything with a 3 at the end, however the radio only takes steps like .40 .42 .45 and I cant set it manually to the .43 as requested.
I can of course do it with through the ATC, but that wouldnt be the true way to do it.
Can anyone tell me how to set the radios to a .43 frequency by using the knobs on the panel, as it would be done in the real world?

Aviation radios don't really use a .03, it is actually .025.  For example the frequencies available would be like below:

121.10
121.125
121.15

Many radios don't show the .005 increment, and simply show as a .02.  For some reason flight sim is rounding up to .03.

Yes, I know, that's why I'm a bit confused about what happens here, I also havent seen it before.
I'm used to series like: .100 - .125 - .150 - .175 or as radios with just 2 decimals will read: .10 - .12 - .15 - .17

However, with that particular flight, yesterday, ATC asked me to switch to, as you say, a rounded up figure of .130 (as was shown in ATC window) which is not in the sequal as the radios allow me to choose from and when I choose either .12(5) or .15(0) I cant call the station I'm handed off to. So if I want to keep the flying experience as it would be in the real world, without the switch option in the ATC-window, I wouldnt be able to contact the next station.

Now I'm a bit confused about what's happening and how to handle it. Is this a bug that can only be overcome by using the switch option in the ATC window? Or is this a real world thing and can I trick the radios to still be able to contact the station by using the .125? Or is there and option that enables me to indeed choose the .130?

Yet another weird thing I noticed. I get handed off to London Centre on 118.475, but in the ATC appears 119.925
Hello Manston Approach!
Again I cant perform the actions given to me and have to rely on the ATC-window to correct the error.
Is there any way to correct these bugs?