Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$62.86	4.617%	$65.7622	$65.76	$65.75	$65.80
Purchase #2	$24.99	11.595%	$27.8876	$27.89	$27.90	$27.90
Purchase #3	$152.32	10.393%	$168.1506	$168.15	$168.15	$168.20
Purchase #4	$161.93	3.301%	$167.2753	$167.28	$167.30	$167.30
Purchase #5	$47.48	4.349%	$49.5449	$49.54	$49.55	$49.50
Purchase #6	$90.72	12.359%	$101.9321	$101.93	$101.95	$101.90
Purchase #7	$171.38	9.656%	$187.9285	$187.93	$187.95	$187.90
7 purchase totals =	$711.68		$768.4812	$768.48	$768.55	$768.50