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	$237.50	4.193%	$247.4584	$247.46	$247.45	$247.50
Purchase #2	$207.61	8.484%	$225.2236	$225.22	$225.20	$225.20
Purchase #3	$168.61	5.753%	$178.3101	$178.31	$178.30	$178.30
Purchase #4	$143.42	11.557%	$159.995	$160.00	$160.00	$160.00
Purchase #5	$173.95	7.509%	$187.0119	$187.01	$187.00	$187.00
Purchase #6	$144.43	5.630%	$152.5614	$152.56	$152.55	$152.60
Purchase #7	$245.77	13.303%	$278.4648	$278.46	$278.45	$278.50
7 purchase totals =	$1,321.29		$1,429.0252	$1,429.02	$1,428.95	$1,429.10