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	$41.57	4.843%	$43.5832	$43.58	$43.60	$43.60
Purchase #2	$220.57	3.742%	$228.8237	$228.82	$228.80	$228.80
Purchase #3	$14.91	5.734%	$15.7649	$15.76	$15.75	$15.80
Purchase #4	$55.67	8.491%	$60.3969	$60.40	$60.40	$60.40
Purchase #5	$109.94	8.660%	$119.4608	$119.46	$119.45	$119.50
Purchase #6	$96.50	10.563%	$106.6933	$106.69	$106.70	$106.70
Purchase #7	$52.55	13.269%	$59.5229	$59.52	$59.50	$59.50
7 purchase totals =	$591.71		$634.2457	$634.23	$634.20	$634.30