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	$225.60	4.575%	$235.9212	$235.92	$235.90	$235.90
Purchase #2	$100.74	10.788%	$111.6078	$111.61	$111.60	$111.60
Purchase #3	$246.86	12.162%	$276.8831	$276.88	$276.90	$276.90
Purchase #4	$35.50	8.614%	$38.558	$38.56	$38.55	$38.60
Purchase #5	$144.51	12.646%	$162.7847	$162.78	$162.80	$162.80
Purchase #6	$239.45	12.605%	$269.6327	$269.63	$269.65	$269.60
Purchase #7	$52.53	13.856%	$59.8086	$59.81	$59.80	$59.80
7 purchase totals =	$1,045.19		$1,155.1961	$1,155.19	$1,155.20	$1,155.20