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	$111.34	6.621%	$118.7118	$118.71	$118.70	$118.70
Purchase #2	$60.29	12.429%	$67.7834	$67.78	$67.80	$67.80
Purchase #3	$150.73	7.788%	$162.4689	$162.47	$162.45	$162.50
Purchase #4	$223.76	8.175%	$242.0524	$242.05	$242.05	$242.10
Purchase #5	$25.57	13.492%	$29.0199	$29.02	$29.00	$29.00
Purchase #6	$242.82	4.366%	$253.4215	$253.42	$253.40	$253.40
Purchase #7	$119.49	11.638%	$133.3962	$133.40	$133.40	$133.40
7 purchase totals =	$934.00		$1,006.8541	$1,006.85	$1,006.80	$1,006.90