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	$146.95	9.451%	$160.8382	$160.84	$160.85	$160.80
Purchase #2	$112.72	7.496%	$121.1695	$121.17	$121.15	$121.20
Purchase #3	$148.46	13.860%	$169.0366	$169.04	$169.05	$169.00
Purchase #4	$131.57	8.507%	$142.7627	$142.76	$142.75	$142.80
Purchase #5	$81.66	9.519%	$89.4332	$89.43	$89.45	$89.40
Purchase #6	$119.49	7.614%	$128.588	$128.59	$128.60	$128.60
Purchase #7	$45.60	6.468%	$48.5494	$48.55	$48.55	$48.50
7 purchase totals =	$786.45		$860.3776	$860.38	$860.40	$860.30