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	$173.78	11.593%	$193.9263	$193.93	$193.95	$193.90
Purchase #2	$200.27	8.856%	$218.0059	$218.01	$218.00	$218.00
Purchase #3	$124.41	13.644%	$141.3845	$141.38	$141.40	$141.40
Purchase #4	$114.81	12.150%	$128.7594	$128.76	$128.75	$128.80
Purchase #5	$49.57	12.680%	$55.8555	$55.86	$55.85	$55.90
Purchase #6	$163.86	5.349%	$172.6249	$172.62	$172.60	$172.60
Purchase #7	$233.45	10.621%	$258.2447	$258.24	$258.25	$258.20
7 purchase totals =	$1,060.15		$1,168.8012	$1,168.80	$1,168.80	$1,168.80