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	$200.48	13.283%	$227.1098	$227.11	$227.10	$227.10
Purchase #2	$73.98	3.138%	$76.3015	$76.30	$76.30	$76.30
Purchase #3	$71.85	4.278%	$74.9237	$74.92	$74.90	$74.90
Purchase #4	$158.69	11.390%	$176.7648	$176.76	$176.75	$176.80
Purchase #5	$172.79	10.830%	$191.5032	$191.50	$191.50	$191.50
Purchase #6	$214.34	3.700%	$222.2706	$222.27	$222.25	$222.30
Purchase #7	$95.72	11.123%	$106.3669	$106.37	$106.35	$106.40
7 purchase totals =	$987.85		$1,075.2405	$1,075.23	$1,075.15	$1,075.30