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	$185.40	5.689%	$195.9474	$195.95	$195.95	$195.90
Purchase #2	$39.66	3.745%	$41.1453	$41.15	$41.15	$41.10
Purchase #3	$246.91	11.560%	$275.4528	$275.45	$275.45	$275.50
Purchase #4	$59.89	10.660%	$66.2743	$66.27	$66.25	$66.30
Purchase #5	$142.38	7.361%	$152.8606	$152.86	$152.85	$152.90
Purchase #6	$47.37	7.149%	$50.7565	$50.76	$50.75	$50.80
Purchase #7	$78.99	6.444%	$84.0801	$84.08	$84.10	$84.10
7 purchase totals =	$800.60		$866.5170	$866.52	$866.50	$866.60