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	$172.70	13.705%	$196.3685	$196.37	$196.35	$196.40
Purchase #2	$159.50	6.785%	$170.3221	$170.32	$170.30	$170.30
Purchase #3	$19.90	11.262%	$22.1411	$22.14	$22.15	$22.10
Purchase #4	$173.95	3.747%	$180.4679	$180.47	$180.45	$180.50
Purchase #5	$184.77	6.451%	$196.6895	$196.69	$196.70	$196.70
Purchase #6	$129.26	9.237%	$141.1997	$141.20	$141.20	$141.20
Purchase #7	$67.65	7.266%	$72.5654	$72.57	$72.55	$72.60
7 purchase totals =	$907.73		$979.7542	$979.76	$979.70	$979.80