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	$111.49	7.256%	$119.5797	$119.58	$119.60	$119.60
Purchase #2	$163.50	10.223%	$180.2146	$180.21	$180.20	$180.20
Purchase #3	$223.58	11.788%	$249.9356	$249.94	$249.95	$249.90
Purchase #4	$224.61	13.870%	$255.7634	$255.76	$255.75	$255.80
Purchase #5	$208.49	5.256%	$219.4482	$219.45	$219.45	$219.40
Purchase #6	$113.50	7.246%	$121.7242	$121.72	$121.70	$121.70
Purchase #7	$30.72	6.855%	$32.8259	$32.83	$32.85	$32.80
7 purchase totals =	$1,075.89		$1,179.4916	$1,179.49	$1,179.50	$1,179.40