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	$59.64	5.113%	$62.6894	$62.69	$62.70	$62.70
Purchase #2	$60.59	10.803%	$67.1355	$67.14	$67.15	$67.10
Purchase #3	$34.28	9.460%	$37.5229	$37.52	$37.50	$37.50
Purchase #4	$102.81	8.762%	$111.8182	$111.82	$111.80	$111.80
Purchase #5	$30.45	5.294%	$32.062	$32.06	$32.05	$32.10
Purchase #6	$204.40	10.407%	$225.6719	$225.67	$225.65	$225.70
Purchase #7	$190.77	3.578%	$197.5958	$197.60	$197.60	$197.60
7 purchase totals =	$682.94		$734.4957	$734.50	$734.45	$734.50