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	$59.50	13.594%	$67.5884	$67.59	$67.60	$67.60
Purchase #2	$233.78	10.242%	$257.7237	$257.72	$257.70	$257.70
Purchase #3	$95.35	5.724%	$100.8078	$100.81	$100.80	$100.80
Purchase #4	$246.29	6.488%	$262.2693	$262.27	$262.25	$262.30
Purchase #5	$114.92	10.164%	$126.6005	$126.60	$126.60	$126.60
Purchase #6	$169.30	9.518%	$185.414	$185.41	$185.40	$185.40
Purchase #7	$28.78	8.482%	$31.2211	$31.22	$31.20	$31.20
7 purchase totals =	$947.92		$1,031.6248	$1,031.62	$1,031.55	$1,031.60