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	$237.51	7.713%	$255.8291	$255.83	$255.85	$255.80
Purchase #2	$20.42	5.142%	$21.47	$21.47	$21.45	$21.50
Purchase #3	$16.26	11.395%	$18.1128	$18.11	$18.10	$18.10
Purchase #4	$107.87	9.626%	$118.2536	$118.25	$118.25	$118.30
Purchase #5	$157.93	5.360%	$166.395	$166.40	$166.40	$166.40
Purchase #6	$16.29	10.758%	$18.0425	$18.04	$18.05	$18.00
Purchase #7	$124.51	10.700%	$137.8326	$137.83	$137.85	$137.80
7 purchase totals =	$680.79		$735.9356	$735.93	$735.95	$735.90