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	$151.75	13.434%	$172.1361	$172.14	$172.15	$172.10
Purchase #2	$72.38	9.782%	$79.4602	$79.46	$79.45	$79.50
Purchase #3	$151.83	5.756%	$160.5693	$160.57	$160.55	$160.60
Purchase #4	$50.80	6.677%	$54.1919	$54.19	$54.20	$54.20
Purchase #5	$131.31	11.339%	$146.1992	$146.20	$146.20	$146.20
Purchase #6	$143.56	4.613%	$150.1824	$150.18	$150.20	$150.20
Purchase #7	$166.79	10.473%	$184.2579	$184.26	$184.25	$184.30
7 purchase totals =	$868.42		$946.9970	$947.00	$947.00	$947.10