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	$85.59	12.335%	$96.1475	$96.15	$96.15	$96.10
Purchase #2	$198.45	6.684%	$211.7144	$211.71	$211.70	$211.70
Purchase #3	$90.55	10.602%	$100.1501	$100.15	$100.15	$100.20
Purchase #4	$196.39	13.120%	$222.1564	$222.16	$222.15	$222.20
Purchase #5	$143.71	11.719%	$160.5514	$160.55	$160.55	$160.60
Purchase #6	$243.61	6.813%	$260.2071	$260.21	$260.20	$260.20
Purchase #7	$9.50	12.639%	$10.7007	$10.70	$10.70	$10.70
7 purchase totals =	$967.80		$1,061.6276	$1,061.63	$1,061.60	$1,061.70