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	$54.49	9.753%	$59.8044	$59.80	$59.80	$59.80
Purchase #2	$104.36	9.779%	$114.5654	$114.57	$114.55	$114.60
Purchase #3	$228.45	12.450%	$256.892	$256.89	$256.90	$256.90
Purchase #4	$21.55	13.800%	$24.5239	$24.52	$24.50	$24.50
Purchase #5	$31.83	8.196%	$34.4388	$34.44	$34.45	$34.40
Purchase #6	$245.88	4.126%	$256.025	$256.03	$256.05	$256.00
Purchase #7	$12.90	5.262%	$13.5788	$13.58	$13.60	$13.60
7 purchase totals =	$699.46		$759.8283	$759.83	$759.85	$759.80