Custom price rounding

We have customers who use the block of time contract, as our global settings are set to round up to 0.5hrs and works for most customers this is unfair to them as a job may only take a couple of minutes. Can we customise these accounts so the time will not be rounded up without it changing the setting globally?
Thanks,

Thank you for posting this. Mmm, rounding settings are global and affect all customers at this time. We will take a note on your question. Thanks.