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	$134.72	11.649%	$150.4135	$150.41	$150.40	$150.40
Purchase #2	$95.95	13.692%	$109.0875	$109.09	$109.10	$109.10
Purchase #3	$81.54	5.782%	$86.2546	$86.25	$86.25	$86.30
Purchase #4	$44.72	8.260%	$48.4139	$48.41	$48.40	$48.40
Purchase #5	$38.92	3.496%	$40.2806	$40.28	$40.30	$40.30
Purchase #6	$174.72	13.433%	$198.1901	$198.19	$198.20	$198.20
Purchase #7	$63.41	5.348%	$66.8012	$66.80	$66.80	$66.80
7 purchase totals =	$633.98		$699.4414	$699.43	$699.45	$699.50