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	$50.62	6.301%	$53.8096	$53.81	$53.80	$53.80
Purchase #2	$18.80	9.418%	$20.5706	$20.57	$20.55	$20.60
Purchase #3	$145.28	11.677%	$162.2443	$162.24	$162.25	$162.20
Purchase #4	$142.40	5.697%	$150.5125	$150.51	$150.50	$150.50
Purchase #5	$12.64	6.283%	$13.4342	$13.43	$13.45	$13.40
Purchase #6	$226.86	3.499%	$234.7978	$234.80	$234.80	$234.80
Purchase #7	$37.29	3.818%	$38.7137	$38.71	$38.70	$38.70
7 purchase totals =	$633.89		$674.0827	$674.07	$674.05	$674.00