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	$173.92	9.262%	$190.0285	$190.03	$190.05	$190.00
Purchase #2	$158.64	4.455%	$165.7074	$165.71	$165.70	$165.70
Purchase #3	$60.86	8.558%	$66.0684	$66.07	$66.05	$66.10
Purchase #4	$243.40	4.423%	$254.1656	$254.17	$254.15	$254.20
Purchase #5	$50.58	10.521%	$55.9015	$55.90	$55.90	$55.90
Purchase #6	$225.84	4.716%	$236.4906	$236.49	$236.50	$236.50
Purchase #7	$124.26	10.304%	$137.0638	$137.06	$137.05	$137.10
7 purchase totals =	$1,037.50		$1,105.4258	$1,105.43	$1,105.40	$1,105.50