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	$239.50	6.538%	$255.1585	$255.16	$255.15	$255.20
Purchase #2	$227.80	7.182%	$244.1606	$244.16	$244.15	$244.20
Purchase #3	$103.30	11.504%	$115.1836	$115.18	$115.20	$115.20
Purchase #4	$82.54	7.528%	$88.7536	$88.75	$88.75	$88.80
Purchase #5	$106.52	7.592%	$114.607	$114.61	$114.60	$114.60
Purchase #6	$186.46	4.287%	$194.4535	$194.45	$194.45	$194.50
Purchase #7	$111.90	10.584%	$123.7435	$123.74	$123.75	$123.70
7 purchase totals =	$1,058.02		$1,136.0603	$1,136.05	$1,136.05	$1,136.20