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	$222.98	7.808%	$240.3903	$240.39	$240.40	$240.40
Purchase #2	$52.38	13.453%	$59.4267	$59.43	$59.45	$59.40
Purchase #3	$158.77	8.621%	$172.4576	$172.46	$172.45	$172.50
Purchase #4	$141.81	8.684%	$154.1248	$154.12	$154.10	$154.10
Purchase #5	$144.75	10.474%	$159.9111	$159.91	$159.90	$159.90
Purchase #6	$177.53	4.231%	$185.0413	$185.04	$185.05	$185.00
Purchase #7	$53.72	8.628%	$58.355	$58.36	$58.35	$58.40
7 purchase totals =	$951.94		$1,029.7068	$1,029.71	$1,029.70	$1,029.70