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	$146.89	3.349%	$151.8093	$151.81	$151.80	$151.80
Purchase #2	$11.45	4.267%	$11.9386	$11.94	$11.95	$11.90
Purchase #3	$247.77	11.240%	$275.6193	$275.62	$275.60	$275.60
Purchase #4	$49.98	4.621%	$52.2896	$52.29	$52.30	$52.30
Purchase #5	$215.74	3.729%	$223.7849	$223.78	$223.80	$223.80
Purchase #6	$118.28	4.675%	$123.8096	$123.81	$123.80	$123.80
Purchase #7	$124.82	7.508%	$134.1915	$134.19	$134.20	$134.20
7 purchase totals =	$914.93		$973.4428	$973.44	$973.45	$973.40