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	$57.76	4.195%	$60.183	$60.18	$60.20	$60.20
Purchase #2	$246.85	3.156%	$254.6406	$254.64	$254.65	$254.60
Purchase #3	$33.45	12.510%	$37.6346	$37.63	$37.65	$37.60
Purchase #4	$214.81	5.647%	$226.9403	$226.94	$226.95	$226.90
Purchase #5	$115.56	4.302%	$120.5314	$120.53	$120.55	$120.50
Purchase #6	$186.78	5.133%	$196.3674	$196.37	$196.35	$196.40
Purchase #7	$151.81	13.210%	$171.8641	$171.86	$171.85	$171.90
7 purchase totals =	$1,007.02		$1,068.1614	$1,068.15	$1,068.20	$1,068.10