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	$242.60	5.794%	$256.6562	$256.66	$256.65	$256.70
Purchase #2	$11.53	8.118%	$12.466	$12.47	$12.45	$12.50
Purchase #3	$31.85	13.708%	$36.216	$36.22	$36.20	$36.20
Purchase #4	$242.90	4.820%	$254.6078	$254.61	$254.60	$254.60
Purchase #5	$192.26	13.131%	$217.5057	$217.51	$217.50	$217.50
Purchase #6	$210.97	10.212%	$232.5143	$232.51	$232.50	$232.50
Purchase #7	$47.31	8.277%	$51.2258	$51.23	$51.25	$51.20
7 purchase totals =	$979.42		$1,061.1918	$1,061.21	$1,061.15	$1,061.20