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	$196.80	13.326%	$223.0256	$223.03	$223.05	$223.00
Purchase #2	$186.50	10.409%	$205.9128	$205.91	$205.90	$205.90
Purchase #3	$233.51	11.559%	$260.5014	$260.50	$260.50	$260.50
Purchase #4	$6.74	5.692%	$7.1236	$7.12	$7.10	$7.10
Purchase #5	$107.78	3.853%	$111.9328	$111.93	$111.95	$111.90
Purchase #6	$130.76	13.313%	$148.1681	$148.17	$148.15	$148.20
Purchase #7	$135.89	5.456%	$143.3042	$143.30	$143.30	$143.30
7 purchase totals =	$997.98		$1,099.9685	$1,099.96	$1,099.95	$1,099.90