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	$67.45	6.651%	$71.9361	$71.94	$71.95	$71.90
Purchase #2	$108.81	10.581%	$120.3232	$120.32	$120.30	$120.30
Purchase #3	$133.75	8.682%	$145.3622	$145.36	$145.35	$145.40
Purchase #4	$103.84	10.231%	$114.4639	$114.46	$114.45	$114.50
Purchase #5	$221.81	10.843%	$245.8609	$245.86	$245.85	$245.90
Purchase #6	$118.70	4.140%	$123.6142	$123.61	$123.60	$123.60
Purchase #7	$177.38	12.340%	$199.2687	$199.27	$199.25	$199.30
7 purchase totals =	$931.74		$1,020.8292	$1,020.82	$1,020.75	$1,020.90