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	$216.54	12.583%	$243.7872	$243.79	$243.80	$243.80
Purchase #2	$148.95	7.102%	$159.5284	$159.53	$159.55	$159.50
Purchase #3	$102.69	8.841%	$111.7688	$111.77	$111.75	$111.80
Purchase #4	$11.57	7.178%	$12.4005	$12.40	$12.40	$12.40
Purchase #5	$204.95	8.697%	$222.7745	$222.77	$222.75	$222.80
Purchase #6	$131.26	5.456%	$138.4215	$138.42	$138.40	$138.40
Purchase #7	$108.54	13.707%	$123.4176	$123.42	$123.40	$123.40
7 purchase totals =	$924.50		$1,012.0985	$1,012.10	$1,012.05	$1,012.10