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	$9.41	6.485%	$10.0202	$10.02	$10.00	$10.00
Purchase #2	$26.35	5.618%	$27.8303	$27.83	$27.85	$27.80
Purchase #3	$165.52	13.592%	$188.0175	$188.02	$188.00	$188.00
Purchase #4	$40.39	13.230%	$45.7336	$45.73	$45.75	$45.70
Purchase #5	$250.58	9.269%	$273.8063	$273.81	$273.80	$273.80
Purchase #6	$208.82	6.866%	$223.1576	$223.16	$223.15	$223.20
Purchase #7	$236.64	8.199%	$256.0421	$256.04	$256.05	$256.00
7 purchase totals =	$937.71		$1,024.6076	$1,024.61	$1,024.60	$1,024.50