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	$141.71	13.415%	$160.7204	$160.72	$160.70	$160.70
Purchase #2	$137.87	12.204%	$154.6957	$154.70	$154.70	$154.70
Purchase #3	$96.62	13.504%	$109.6676	$109.67	$109.65	$109.70
Purchase #4	$141.62	6.748%	$151.1765	$151.18	$151.20	$151.20
Purchase #5	$182.43	4.599%	$190.82	$190.82	$190.80	$190.80
Purchase #6	$55.33	4.622%	$57.8874	$57.89	$57.90	$57.90
Purchase #7	$66.40	9.212%	$72.5168	$72.52	$72.50	$72.50
7 purchase totals =	$821.98		$897.4844	$897.50	$897.45	$897.50