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	$230.25	11.189%	$256.0127	$256.01	$256.00	$256.00
Purchase #2	$53.87	9.807%	$59.153	$59.15	$59.15	$59.20
Purchase #3	$62.99	7.289%	$67.5813	$67.58	$67.60	$67.60
Purchase #4	$248.31	7.338%	$266.531	$266.53	$266.55	$266.50
Purchase #5	$50.63	6.827%	$54.0865	$54.09	$54.10	$54.10
Purchase #6	$230.41	8.600%	$250.2253	$250.23	$250.25	$250.20
Purchase #7	$112.89	4.778%	$118.2839	$118.28	$118.30	$118.30
7 purchase totals =	$989.35		$1,071.8737	$1,071.87	$1,071.95	$1,071.90