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	$195.73	13.537%	$222.226	$222.23	$222.25	$222.20
Purchase #2	$25.83	12.666%	$29.1016	$29.10	$29.10	$29.10
Purchase #3	$113.39	5.364%	$119.4722	$119.47	$119.45	$119.50
Purchase #4	$111.25	4.478%	$116.2318	$116.23	$116.25	$116.20
Purchase #5	$104.59	13.460%	$118.6678	$118.67	$118.65	$118.70
Purchase #6	$121.73	8.213%	$131.7277	$131.73	$131.75	$131.70
Purchase #7	$12.27	10.660%	$13.578	$13.58	$13.60	$13.60
7 purchase totals =	$684.79		$751.0051	$751.01	$751.05	$751.00