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	$42.48	9.718%	$46.6082	$46.61	$46.60	$46.60
Purchase #2	$52.51	5.466%	$55.3802	$55.38	$55.40	$55.40
Purchase #3	$11.28	6.805%	$12.0476	$12.05	$12.05	$12.00
Purchase #4	$100.90	10.821%	$111.8184	$111.82	$111.80	$111.80
Purchase #5	$182.61	4.859%	$191.483	$191.48	$191.50	$191.50
Purchase #6	$12.61	6.755%	$13.4618	$13.46	$13.45	$13.50
Purchase #7	$29.55	12.244%	$33.1681	$33.17	$33.15	$33.20
7 purchase totals =	$431.94		$463.9673	$463.97	$463.95	$464.00