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	$93.85	4.485%	$98.0592	$98.06	$98.05	$98.10
Purchase #2	$124.75	5.151%	$131.1759	$131.18	$131.20	$131.20
Purchase #3	$34.88	10.525%	$38.5511	$38.55	$38.55	$38.60
Purchase #4	$13.99	12.679%	$15.7638	$15.76	$15.75	$15.80
Purchase #5	$52.75	3.531%	$54.6126	$54.61	$54.60	$54.60
Purchase #6	$198.38	5.443%	$209.1778	$209.18	$209.20	$209.20
Purchase #7	$56.58	5.104%	$59.4678	$59.47	$59.45	$59.50
7 purchase totals =	$575.18		$606.8082	$606.81	$606.80	$607.00