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	$42.75	9.234%	$46.6975	$46.70	$46.70	$46.70
Purchase #2	$193.85	4.177%	$201.9471	$201.95	$201.95	$201.90
Purchase #3	$98.78	12.528%	$111.1552	$111.16	$111.15	$111.20
Purchase #4	$233.35	6.221%	$247.8667	$247.87	$247.85	$247.90
Purchase #5	$224.54	13.826%	$255.5849	$255.58	$255.60	$255.60
Purchase #6	$85.42	6.126%	$90.6528	$90.65	$90.65	$90.70
Purchase #7	$191.37	13.826%	$217.8288	$217.83	$217.85	$217.80
7 purchase totals =	$1,070.06		$1,171.7330	$1,171.74	$1,171.75	$1,171.80