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	$160.58	5.128%	$168.8145	$168.81	$168.80	$168.80
Purchase #2	$173.96	10.194%	$191.6935	$191.69	$191.70	$191.70
Purchase #3	$74.44	11.748%	$83.1852	$83.19	$83.20	$83.20
Purchase #4	$84.27	5.794%	$89.1526	$89.15	$89.15	$89.20
Purchase #5	$103.65	7.352%	$111.2703	$111.27	$111.25	$111.30
Purchase #6	$10.55	11.484%	$11.7616	$11.76	$11.75	$11.80
Purchase #7	$106.86	9.364%	$116.8664	$116.87	$116.85	$116.90
7 purchase totals =	$714.31		$772.7441	$772.74	$772.70	$772.90