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	$191.82	13.581%	$217.8711	$217.87	$217.85	$217.90
Purchase #2	$54.77	7.268%	$58.7507	$58.75	$58.75	$58.80
Purchase #3	$237.58	5.191%	$249.9128	$249.91	$249.90	$249.90
Purchase #4	$122.83	13.730%	$139.6946	$139.69	$139.70	$139.70
Purchase #5	$233.64	10.439%	$258.0297	$258.03	$258.05	$258.00
Purchase #6	$213.52	9.178%	$233.1169	$233.12	$233.10	$233.10
Purchase #7	$57.54	3.233%	$59.4003	$59.40	$59.40	$59.40
7 purchase totals =	$1,111.70		$1,216.7761	$1,216.77	$1,216.75	$1,216.80