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	$111.56	3.719%	$115.7089	$115.71	$115.70	$115.70
Purchase #2	$92.48	3.668%	$95.8722	$95.87	$95.85	$95.90
Purchase #3	$196.69	10.395%	$217.1359	$217.14	$217.15	$217.10
Purchase #4	$195.36	9.814%	$214.5326	$214.53	$214.55	$214.50
Purchase #5	$57.35	4.286%	$59.808	$59.81	$59.80	$59.80
Purchase #6	$248.54	8.341%	$269.2707	$269.27	$269.25	$269.30
Purchase #7	$242.78	11.754%	$271.3164	$271.32	$271.30	$271.30
7 purchase totals =	$1,144.76		$1,243.6447	$1,243.65	$1,243.60	$1,243.60