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	$43.49	7.685%	$46.8322	$46.83	$46.85	$46.80
Purchase #2	$135.87	5.609%	$143.4909	$143.49	$143.50	$143.50
Purchase #3	$55.43	12.547%	$62.3848	$62.38	$62.40	$62.40
Purchase #4	$190.37	4.503%	$198.9424	$198.94	$198.95	$198.90
Purchase #5	$117.56	9.205%	$128.3814	$128.38	$128.40	$128.40
Purchase #6	$139.43	3.394%	$144.1623	$144.16	$144.15	$144.20
Purchase #7	$218.25	10.687%	$241.5744	$241.57	$241.55	$241.60
7 purchase totals =	$900.40		$965.7684	$965.75	$965.80	$965.80