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	$104.77	9.462%	$114.6833	$114.68	$114.70	$114.70
Purchase #2	$152.60	3.733%	$158.2966	$158.30	$158.30	$158.30
Purchase #3	$72.56	12.549%	$81.6656	$81.67	$81.65	$81.70
Purchase #4	$222.82	6.137%	$236.4945	$236.49	$236.50	$236.50
Purchase #5	$195.41	8.387%	$211.799	$211.80	$211.80	$211.80
Purchase #6	$85.88	5.341%	$90.4669	$90.47	$90.45	$90.50
Purchase #7	$247.86	10.434%	$273.7217	$273.72	$273.70	$273.70
7 purchase totals =	$1,081.90		$1,167.1276	$1,167.13	$1,167.10	$1,167.20