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	$68.27	6.248%	$72.5355	$72.54	$72.55	$72.50
Purchase #2	$62.62	7.410%	$67.2601	$67.26	$67.25	$67.30
Purchase #3	$86.54	4.446%	$90.3876	$90.39	$90.40	$90.40
Purchase #4	$21.72	4.726%	$22.7465	$22.75	$22.75	$22.70
Purchase #5	$231.98	6.716%	$247.5598	$247.56	$247.55	$247.60
Purchase #6	$97.70	13.249%	$110.6443	$110.64	$110.65	$110.60
Purchase #7	$58.95	8.804%	$64.14	$64.14	$64.15	$64.10
7 purchase totals =	$627.78		$675.2738	$675.28	$675.30	$675.20