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	$151.35	3.338%	$156.4021	$156.40	$156.40	$156.40
Purchase #2	$43.87	5.128%	$46.1197	$46.12	$46.10	$46.10
Purchase #3	$44.96	12.813%	$50.7207	$50.72	$50.70	$50.70
Purchase #4	$215.67	5.520%	$227.575	$227.58	$227.60	$227.60
Purchase #5	$38.52	9.663%	$42.2422	$42.24	$42.25	$42.20
Purchase #6	$110.44	5.752%	$116.7925	$116.79	$116.80	$116.80
Purchase #7	$40.61	7.679%	$43.7284	$43.73	$43.75	$43.70
7 purchase totals =	$645.42		$683.5806	$683.58	$683.60	$683.50