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	$60.53	11.451%	$67.4613	$67.46	$67.45	$67.50
Purchase #2	$107.43	12.287%	$120.6299	$120.63	$120.65	$120.60
Purchase #3	$77.56	12.797%	$87.4854	$87.49	$87.50	$87.50
Purchase #4	$99.72	12.717%	$112.4014	$112.40	$112.40	$112.40
Purchase #5	$110.79	3.322%	$114.4704	$114.47	$114.45	$114.50
Purchase #6	$122.27	7.773%	$131.774	$131.77	$131.75	$131.80
Purchase #7	$142.97	6.213%	$151.8527	$151.85	$151.85	$151.90
7 purchase totals =	$721.27		$786.0751	$786.07	$786.05	$786.20