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	$233.28	9.732%	$255.9828	$255.98	$256.00	$256.00
Purchase #2	$89.35	5.537%	$94.2973	$94.30	$94.30	$94.30
Purchase #3	$73.92	11.600%	$82.4947	$82.49	$82.50	$82.50
Purchase #4	$91.42	8.149%	$98.8698	$98.87	$98.85	$98.90
Purchase #5	$42.98	10.102%	$47.3218	$47.32	$47.30	$47.30
Purchase #6	$204.51	6.220%	$217.2305	$217.23	$217.25	$217.20
Purchase #7	$134.58	12.315%	$151.1535	$151.15	$151.15	$151.20
7 purchase totals =	$870.04		$947.3504	$947.34	$947.35	$947.40