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	$220.40	9.199%	$240.6746	$240.67	$240.65	$240.70
Purchase #2	$122.31	13.319%	$138.6005	$138.60	$138.60	$138.60
Purchase #3	$140.83	10.268%	$155.2904	$155.29	$155.30	$155.30
Purchase #4	$68.80	5.143%	$72.3384	$72.34	$72.35	$72.30
Purchase #5	$241.68	11.499%	$269.4708	$269.47	$269.45	$269.50
Purchase #6	$111.53	7.338%	$119.7141	$119.71	$119.70	$119.70
Purchase #7	$94.65	6.523%	$100.824	$100.82	$100.80	$100.80
7 purchase totals =	$1,000.20		$1,096.9128	$1,096.90	$1,096.85	$1,096.90