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	$180.60	6.489%	$192.3191	$192.32	$192.30	$192.30
Purchase #2	$133.35	7.710%	$143.6313	$143.63	$143.65	$143.60
Purchase #3	$61.90	7.372%	$66.4633	$66.46	$66.45	$66.50
Purchase #4	$189.83	12.164%	$212.9209	$212.92	$212.90	$212.90
Purchase #5	$103.35	12.246%	$116.0062	$116.01	$116.00	$116.00
Purchase #6	$140.49	4.443%	$146.732	$146.73	$146.75	$146.70
Purchase #7	$139.60	10.641%	$154.4548	$154.45	$154.45	$154.50
7 purchase totals =	$949.12		$1,032.5276	$1,032.52	$1,032.50	$1,032.50