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	$154.86	11.161%	$172.1439	$172.14	$172.15	$172.10
Purchase #2	$57.83	10.233%	$63.7477	$63.75	$63.75	$63.70
Purchase #3	$64.81	3.334%	$66.9708	$66.97	$66.95	$67.00
Purchase #4	$62.48	6.107%	$66.2957	$66.30	$66.30	$66.30
Purchase #5	$247.41	11.480%	$275.8127	$275.81	$275.80	$275.80
Purchase #6	$203.42	9.163%	$222.0594	$222.06	$222.05	$222.10
Purchase #7	$65.30	12.697%	$73.5911	$73.59	$73.60	$73.60
7 purchase totals =	$856.11		$940.6213	$940.62	$940.60	$940.60