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	$191.98	10.516%	$212.1686	$212.17	$212.15	$212.20
Purchase #2	$34.33	12.115%	$38.4891	$38.49	$38.50	$38.50
Purchase #3	$51.85	5.195%	$54.5436	$54.54	$54.55	$54.50
Purchase #4	$91.28	10.298%	$100.68	$100.68	$100.70	$100.70
Purchase #5	$144.81	4.573%	$151.4322	$151.43	$151.45	$151.40
Purchase #6	$76.40	8.683%	$83.0338	$83.03	$83.05	$83.00
Purchase #7	$130.50	12.278%	$146.5228	$146.52	$146.50	$146.50
7 purchase totals =	$721.15		$786.8701	$786.86	$786.90	$786.80