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	$102.49	8.449%	$111.1494	$111.15	$111.15	$111.10
Purchase #2	$136.79	8.218%	$148.0314	$148.03	$148.05	$148.00
Purchase #3	$60.82	11.723%	$67.9499	$67.95	$67.95	$67.90
Purchase #4	$44.80	5.278%	$47.1645	$47.16	$47.15	$47.20
Purchase #5	$209.72	12.853%	$236.6753	$236.68	$236.70	$236.70
Purchase #6	$134.88	11.788%	$150.7797	$150.78	$150.80	$150.80
Purchase #7	$76.40	11.335%	$85.0599	$85.06	$85.05	$85.10
7 purchase totals =	$765.90		$846.8101	$846.81	$846.85	$846.80