Having established a reputation as a big meanie, I have not really had problems with late in the day tax payments.
However, POSTMARKS are another thing entirely.  The Town voted about 5 years ago to NOT accept postmarks.  (Article itself was worded 'positively.') This has been a wonderful thing because technically one would have to wait to do the Delq. Warrant until taxes postmarked the due date arrived from Hawaii or where ever including ones which might have the wrong or no zip code.  Even then it is truly up to the Delinquent Collector to adjust out the Int and Penalties.  
This decision had been percolating for a few years and when a very large escrow check which had been indeed sent out on the right day, but through a set of science-fiction  style events, arrived almost 3 weeks late - it was time for the No Postmark article.
The Delinquent Collector and I eased first two years with a bit of common sense graciousness (while watching carefully for repeaters).  The bills have "Postmarks Not accepted - taxes due in hand" printed on them plus a new little sentence which also 'graciously' points out that the P.O. 
This is probably most relevant to once a year collecting towns.
Miki - Treasurer, Townshend