Hi there 
My problem:
HomeKit shows current temperatures rounded to the next half or full degree, even if no value step is set.
My system:
Summary
#########################################################################
############### openhabian ############################################
#########################################################################
## Ip = xxx.xxx.xxx.xxx
## Release = Raspbian GNU/Linux 11 (bullseye)
## Kernel = Linux 6.1.21-v7+
## Platform = Raspberry Pi 3 Model B Plus Rev 1.3
## Uptime = 1 day(s). 15:37:21
## CPU Usage = 3.28% avg over 4 cpu(s) (4 core(s) x 1 socket(s))
## CPU Load = 1m: 0.55, 5m: 0.31, 15m: 0.22
## Memory = Free: 0.10GB (11%), Used: 0.84GB (89%), Total: 0.94GB
## Swap = Free: 2.21GB (97%), Used: 0.07GB (3%), Total: 2.29GB
## Root = Free: 18.10GB (65%), Used: 9.66GB (35%), Total: 28.98GB
## Updates = 0 apt updates available.
## Sessions = 1 session(s)
## Processes = 136 running processes of 32768 maximum processes
#########################################################################
What I have done:
I moved from textual configurations to the UI config to use the Semantic Model. I created the items from things and added the metadata for HomeKit.
For Thermostat.CurrentTemperature I added no further config but then the values displayed in HomeKit are set to a step of 0.5 what is too inexact for my favor.
I also tried to add a config step, but the UI shows a form validation error (see screenshot below).
I tried adding the value for steps into the code column like this
value: Thermostat.CurrentTemperature
config:
step: 0.1
and even 
value: Thermostat.CurrentTemperature
config:
step: 0,1
but both without any change in HomeKit. 
In my .items-file it looked like this and was showing the actual value:
Number OG_Arbeitszimmer_Heizung_Ist_Temp "Arbeitszimmer Heizung ist-Temp" (gOG_Arbeitszimmer_Heizung, INNOGY_Temp, OG_Arbeitszimmer, gSollIstVergleich) {homekit = "CurrentTemperature"}
Any help is highly appreciated.
(wife acceptance factor is decreasing rapidly 
)