Do skills use fractional seconds?

Do skills use fractional seconds? Like if an enchant increases hexes duration by 42%, and you use it with a 8 second hex, does that increase the hex duration to 11.36 seconds or only 11 seconds?

I do believe the game rounds to the tenth. >5 rounds up, <4 rounds down.

Game rounds to whole seconds except for some oddball skills.

Patient Spirit is one of those. With a 20% enchanting weapon, the duration would be 2.4 seconds but this is rounded to 3 seconds.

Actually, I don't think we really know. It would be very difficult to properly test. There are lots of people who say they have tested such things, but most of the tests involving fractional results have been done either using a stopwatch and/or by observing animations or damage numbers. In both cases, the observed results - skill animations and damage numbers - may not accurately reflect the actual results generated by the software itself.
In other words, the animations may, for example, make something appear to last 2 seconds, but, in-game the affect may last 2.4 or whatever. No one really knows except the software designers, and they're not telling.

well from my testing, durations are rounded to nearest whole number.
.5 are rounded up, anything under that is rounded down

casting time is different though. it uses some sort of fractional system