If you want to round to the nearest year
IF(
{Continuous Service Date},
ROUND(DATETIME_DIFF(TODAY(), {Continuous Service Date}, "months")/12)
)
^I used TODAY instead of NOW because you are calculating years. You don’t need the formulas to refresh frequently, so using TODAY will be more efficient.
If you want to always round up:
IF(
{Continuous Service Date},
ROUNDUP(DATETIME_DIFF(TODAY(), {Continuous Service Date}, "months")/12, 0)
)