In the US, the AR30 should be in CU mode out of the box and there should not be a problem with the tuning steps. But if, for example, a factory reset has been carried out, then the unit will power back up in EU mode.
In EU mode, the unit defaults to EU FM/AM band, which tunes in different kHz jumps to CU mode. By setting the AR30 back to CU mode as detailed below, the unit will switch back to CU FM/AM band which will correct the tuning steps.
To return the AR30 to CU mode, you will will need to press & hold down the BAND button on power up (at the rear mains switch) which will switch the unit to CU FM/AM mode. The unit will display Region CU on power up.