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	$107.82	5.787%	$114.0595	$114.06	$114.05	$114.10
Purchase #2	$240.43	13.726%	$273.4314	$273.43	$273.45	$273.40
Purchase #3	$217.38	11.561%	$242.5113	$242.51	$242.50	$242.50
Purchase #4	$89.78	6.668%	$95.7665	$95.77	$95.75	$95.80
Purchase #5	$143.38	7.698%	$154.4174	$154.42	$154.40	$154.40
Purchase #6	$163.93	6.243%	$174.1641	$174.16	$174.15	$174.20
Purchase #7	$111.79	12.868%	$126.1751	$126.18	$126.20	$126.20
7 purchase totals =	$1,074.51		$1,180.5253	$1,180.53	$1,180.50	$1,180.60