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	$134.62	9.187%	$146.9875	$146.99	$147.00	$147.00
Purchase #2	$130.32	8.826%	$141.822	$141.82	$141.80	$141.80
Purchase #3	$18.86	3.479%	$19.5161	$19.52	$19.50	$19.50
Purchase #4	$88.34	6.849%	$94.3904	$94.39	$94.40	$94.40
Purchase #5	$18.70	10.404%	$20.6455	$20.65	$20.65	$20.60
Purchase #6	$154.46	12.246%	$173.3752	$173.38	$173.40	$173.40
Purchase #7	$134.85	5.313%	$142.0146	$142.01	$142.00	$142.00
7 purchase totals =	$680.15		$738.7513	$738.76	$738.75	$738.70