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	$143.83	12.491%	$161.7958	$161.80	$161.80	$161.80
Purchase #2	$106.90	4.123%	$111.3075	$111.31	$111.30	$111.30
Purchase #3	$217.85	12.209%	$244.4473	$244.45	$244.45	$244.40
Purchase #4	$187.56	3.358%	$193.8583	$193.86	$193.85	$193.90
Purchase #5	$172.59	13.390%	$195.6998	$195.70	$195.70	$195.70
Purchase #6	$74.80	10.223%	$82.4468	$82.45	$82.45	$82.40
Purchase #7	$163.48	5.308%	$172.1575	$172.16	$172.15	$172.20
7 purchase totals =	$1,067.01		$1,161.7130	$1,161.73	$1,161.70	$1,161.70