Why condiments expiry date is rounded?
Food quality isn't binary; it doesn't go from perfectly good to perfectly bad in an instant. Even if it did, the time it would take depends on the storage temperature. And for non-liquid foods, it's possible that only a part went bad (how well does it mix?). 

So, you don't get a precise date, but a rough interval at which time the decay starts to set in. As a result, the manufacturer will just pick a rounded date from that interval.

Example: the engineers might calculate that under reasonable circumstances, the product may start to noticably deteriorate after 52-75 days, and become dangerous after 81-112 days. They manufacturer could then say that the expiry date would be 60 days.

(The other answers explain why you'd use the first interval, but not why they're actually intervals.)

:edit:

The likely reason why they're all the same 60 days is probably also engineering. How much preservative do they use? As noted in the comments, the primary preservatives are the acids, but you need quite some sugar to compensate. It seems 60 days is a commonly accepted balance.