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	$174.31	9.511%	$190.8886	$190.89	$190.90	$190.90
Purchase #2	$80.95	3.277%	$83.6027	$83.60	$83.60	$83.60
Purchase #3	$212.33	13.595%	$241.1963	$241.20	$241.20	$241.20
Purchase #4	$60.58	6.281%	$64.385	$64.39	$64.40	$64.40
Purchase #5	$40.71	3.244%	$42.0306	$42.03	$42.05	$42.00
Purchase #6	$100.91	10.575%	$111.5812	$111.58	$111.60	$111.60
Purchase #7	$137.81	10.175%	$151.8322	$151.83	$151.85	$151.80
7 purchase totals =	$807.60		$885.5166	$885.52	$885.60	$885.50