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	$116.35	9.492%	$127.3939	$127.39	$127.40	$127.40
Purchase #2	$85.77	11.329%	$95.4869	$95.49	$95.50	$95.50
Purchase #3	$18.73	5.677%	$19.7933	$19.79	$19.80	$19.80
Purchase #4	$219.52	11.855%	$245.5441	$245.54	$245.55	$245.50
Purchase #5	$126.50	8.188%	$136.8578	$136.86	$136.85	$136.90
Purchase #6	$11.41	12.708%	$12.86	$12.86	$12.85	$12.90
Purchase #7	$148.47	11.480%	$165.5144	$165.51	$165.50	$165.50
7 purchase totals =	$726.75		$803.4504	$803.44	$803.45	$803.50