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	$67.48	8.305%	$73.0842	$73.08	$73.10	$73.10
Purchase #2	$246.38	3.858%	$255.8853	$255.89	$255.90	$255.90
Purchase #3	$14.34	8.105%	$15.5023	$15.50	$15.50	$15.50
Purchase #4	$248.80	4.815%	$260.7797	$260.78	$260.80	$260.80
Purchase #5	$132.98	4.574%	$139.0625	$139.06	$139.05	$139.10
Purchase #6	$26.57	5.822%	$28.1169	$28.12	$28.10	$28.10
Purchase #7	$50.35	3.546%	$52.1354	$52.14	$52.15	$52.10
7 purchase totals =	$786.90		$824.5663	$824.57	$824.60	$824.60