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	$133.27	8.564%	$144.6832	$144.68	$144.70	$144.70
Purchase #2	$224.65	13.767%	$255.5776	$255.58	$255.60	$255.60
Purchase #3	$140.90	3.283%	$145.5257	$145.53	$145.55	$145.50
Purchase #4	$116.69	6.583%	$124.3717	$124.37	$124.35	$124.40
Purchase #5	$161.70	10.533%	$178.7319	$178.73	$178.75	$178.70
Purchase #6	$52.42	3.272%	$54.1352	$54.14	$54.15	$54.10
Purchase #7	$161.83	12.390%	$181.8807	$181.88	$181.90	$181.90
7 purchase totals =	$991.46		$1,084.9060	$1,084.91	$1,085.00	$1,084.90