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	$91.70	3.738%	$95.1277	$95.13	$95.15	$95.10
Purchase #2	$132.42	8.489%	$143.6611	$143.66	$143.65	$143.70
Purchase #3	$128.67	10.440%	$142.1031	$142.10	$142.10	$142.10
Purchase #4	$150.91	3.188%	$155.721	$155.72	$155.70	$155.70
Purchase #5	$69.27	4.757%	$72.5652	$72.57	$72.55	$72.60
Purchase #6	$151.45	4.670%	$158.5227	$158.52	$158.50	$158.50
Purchase #7	$100.54	4.413%	$104.9768	$104.98	$105.00	$105.00
7 purchase totals =	$824.96		$872.6776	$872.68	$872.65	$872.70