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	$230.67	10.657%	$255.2525	$255.25	$255.25	$255.30
Purchase #2	$127.36	4.762%	$133.4249	$133.42	$133.40	$133.40
Purchase #3	$55.69	12.644%	$62.7314	$62.73	$62.75	$62.70
Purchase #4	$82.87	8.787%	$90.1518	$90.15	$90.15	$90.20
Purchase #5	$158.33	9.675%	$173.6484	$173.65	$173.65	$173.60
Purchase #6	$185.76	7.715%	$200.0914	$200.09	$200.10	$200.10
Purchase #7	$12.84	11.567%	$14.3252	$14.33	$14.35	$14.30
7 purchase totals =	$853.52		$929.6256	$929.62	$929.65	$929.60