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	$162.43	3.735%	$168.4968	$168.50	$168.50	$168.50
Purchase #2	$12.89	12.235%	$14.4671	$14.47	$14.45	$14.50
Purchase #3	$21.78	9.506%	$23.8504	$23.85	$23.85	$23.90
Purchase #4	$100.76	7.165%	$107.9795	$107.98	$108.00	$108.00
Purchase #5	$103.28	8.292%	$111.844	$111.84	$111.85	$111.80
Purchase #6	$40.84	10.118%	$44.9722	$44.97	$44.95	$45.00
Purchase #7	$195.93	6.388%	$208.446	$208.45	$208.45	$208.40
7 purchase totals =	$637.91		$680.0560	$680.06	$680.05	$680.10