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	$162.34	11.256%	$180.613	$180.61	$180.60	$180.60
Purchase #2	$111.76	11.596%	$124.7197	$124.72	$124.70	$124.70
Purchase #3	$224.89	3.835%	$233.5145	$233.51	$233.50	$233.50
Purchase #4	$99.75	6.683%	$106.4163	$106.42	$106.40	$106.40
Purchase #5	$229.62	4.717%	$240.4512	$240.45	$240.45	$240.50
Purchase #6	$149.47	10.740%	$165.5231	$165.52	$165.50	$165.50
Purchase #7	$42.64	7.283%	$45.7455	$45.75	$45.75	$45.70
7 purchase totals =	$1,020.47		$1,096.9833	$1,096.98	$1,096.90	$1,096.90