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	$36.45	11.445%	$40.6217	$40.62	$40.60	$40.60
Purchase #2	$212.71	13.326%	$241.0557	$241.06	$241.05	$241.10
Purchase #3	$215.58	12.113%	$241.6932	$241.69	$241.70	$241.70
Purchase #4	$10.36	10.852%	$11.4843	$11.48	$11.50	$11.50
Purchase #5	$238.27	7.559%	$256.2808	$256.28	$256.30	$256.30
Purchase #6	$200.84	5.743%	$212.3742	$212.37	$212.35	$212.40
Purchase #7	$12.76	8.119%	$13.796	$13.80	$13.80	$13.80
7 purchase totals =	$926.97		$1,017.3059	$1,017.30	$1,017.30	$1,017.40