Your question doesn’t make sense!
If you’re after (TAI-UTC), then that’s not an observed quantity. It’s defined by when leap seconds are inserted. A simple list of leap seconds over recent years will give you an answer that is 100% accurate by definition:
The current value is precisely 37 seconds.
But… if you’re after UT1-UTC (I can’t quite think why you would be – it’s only relevant to rising and setting times!), the full gory details are all here with awful lot of decimal places (see Bulletin A):
However, UT1-UTC is maintained at a value less than 0.5 seconds by inserting leap seconds whenever it drifts outside that range. If, as you say, you are only interested in accuracy to the nearest second, then you can assume that UT1-UTC always equals zero.