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	$114.55	13.703%	$130.2468	$130.25	$130.25	$130.20
Purchase #2	$50.92	6.515%	$54.2374	$54.24	$54.25	$54.20
Purchase #3	$208.39	4.785%	$218.3615	$218.36	$218.35	$218.40
Purchase #4	$77.46	10.810%	$85.8334	$85.83	$85.85	$85.80
Purchase #5	$47.36	8.123%	$51.2071	$51.21	$51.20	$51.20
Purchase #6	$90.89	11.873%	$101.6814	$101.68	$101.70	$101.70
Purchase #7	$62.60	7.782%	$67.4715	$67.47	$67.45	$67.50
7 purchase totals =	$652.17		$709.0391	$709.04	$709.05	$709.00