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	$238.35	7.473%	$256.1619	$256.16	$256.15	$256.20
Purchase #2	$70.91	9.296%	$77.5018	$77.50	$77.50	$77.50
Purchase #3	$164.53	11.720%	$183.8129	$183.81	$183.80	$183.80
Purchase #4	$118.82	10.458%	$131.2462	$131.25	$131.25	$131.20
Purchase #5	$87.72	3.843%	$91.0911	$91.09	$91.10	$91.10
Purchase #6	$143.84	5.612%	$151.9123	$151.91	$151.90	$151.90
Purchase #7	$114.51	6.115%	$121.5123	$121.51	$121.50	$121.50
7 purchase totals =	$938.68		$1,013.2385	$1,013.23	$1,013.20	$1,013.20