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	$248.70	5.414%	$262.1646	$262.16	$262.15	$262.20
Purchase #2	$233.39	3.330%	$241.1619	$241.16	$241.15	$241.20
Purchase #3	$118.64	12.861%	$133.8983	$133.90	$133.90	$133.90
Purchase #4	$211.63	3.434%	$218.8974	$218.90	$218.90	$218.90
Purchase #5	$130.62	12.196%	$146.5504	$146.55	$146.55	$146.60
Purchase #6	$11.60	7.191%	$12.4342	$12.43	$12.45	$12.40
Purchase #7	$214.53	11.328%	$238.832	$238.83	$238.85	$238.80
7 purchase totals =	$1,169.11		$1,253.9388	$1,253.93	$1,253.95	$1,254.00