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	$196.96	13.500%	$223.5496	$223.55	$223.55	$223.50
Purchase #2	$95.36	6.158%	$101.2323	$101.23	$101.25	$101.20
Purchase #3	$36.61	8.261%	$39.6344	$39.63	$39.65	$39.60
Purchase #4	$176.81	11.237%	$196.6781	$196.68	$196.70	$196.70
Purchase #5	$221.98	8.338%	$240.4887	$240.49	$240.50	$240.50
Purchase #6	$66.42	6.459%	$70.7101	$70.71	$70.70	$70.70
Purchase #7	$64.60	4.613%	$67.58	$67.58	$67.60	$67.60
7 purchase totals =	$858.74		$939.8732	$939.87	$939.95	$939.80