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	$57.94	3.242%	$59.8184	$59.82	$59.80	$59.80
Purchase #2	$193.42	12.290%	$217.1913	$217.19	$217.20	$217.20
Purchase #3	$224.83	7.421%	$241.5146	$241.51	$241.50	$241.50
Purchase #4	$18.36	13.558%	$20.8492	$20.85	$20.85	$20.80
Purchase #5	$102.77	8.537%	$111.5435	$111.54	$111.55	$111.50
Purchase #6	$45.66	5.508%	$48.175	$48.18	$48.20	$48.20
Purchase #7	$25.26	11.359%	$28.1293	$28.13	$28.15	$28.10
7 purchase totals =	$668.24		$727.2213	$727.22	$727.25	$727.10