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	$67.57	5.311%	$71.1586	$71.16	$71.15	$71.20
Purchase #2	$39.60	10.233%	$43.6523	$43.65	$43.65	$43.70
Purchase #3	$50.28	4.350%	$52.4672	$52.47	$52.45	$52.50
Purchase #4	$44.41	5.210%	$46.7238	$46.72	$46.70	$46.70
Purchase #5	$182.79	9.316%	$199.8187	$199.82	$199.80	$199.80
Purchase #6	$48.52	11.785%	$54.2381	$54.24	$54.25	$54.20
Purchase #7	$16.49	11.684%	$18.4167	$18.42	$18.40	$18.40
7 purchase totals =	$449.66		$486.4754	$486.48	$486.40	$486.50