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	$61.79	8.119%	$66.8067	$66.81	$66.80	$66.80
Purchase #2	$108.86	6.614%	$116.06	$116.06	$116.05	$116.10
Purchase #3	$95.97	9.182%	$104.782	$104.78	$104.80	$104.80
Purchase #4	$28.70	13.732%	$32.6411	$32.64	$32.65	$32.60
Purchase #5	$185.89	11.296%	$206.8881	$206.89	$206.90	$206.90
Purchase #6	$117.73	3.841%	$122.252	$122.25	$122.25	$122.30
Purchase #7	$39.89	7.820%	$43.0094	$43.01	$43.00	$43.00
7 purchase totals =	$638.83		$692.4393	$692.44	$692.45	$692.50