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	$222.78	5.533%	$235.1064	$235.11	$235.10	$235.10
Purchase #2	$45.76	6.158%	$48.5779	$48.58	$48.60	$48.60
Purchase #3	$201.97	9.678%	$221.5167	$221.52	$221.50	$221.50
Purchase #4	$250.85	10.765%	$277.854	$277.85	$277.85	$277.90
Purchase #5	$59.89	11.724%	$66.9115	$66.91	$66.90	$66.90
Purchase #6	$195.25	10.268%	$215.2983	$215.30	$215.30	$215.30
Purchase #7	$137.39	6.797%	$146.7284	$146.73	$146.75	$146.70
7 purchase totals =	$1,113.89		$1,211.9932	$1,212.00	$1,212.00	$1,212.00