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	$95.45	3.255%	$98.5569	$98.56	$98.55	$98.60
Purchase #2	$37.43	8.377%	$40.5655	$40.57	$40.55	$40.60
Purchase #3	$118.72	3.734%	$123.153	$123.15	$123.15	$123.20
Purchase #4	$39.82	10.693%	$44.078	$44.08	$44.10	$44.10
Purchase #5	$13.98	13.195%	$15.8247	$15.82	$15.80	$15.80
Purchase #6	$209.81	7.131%	$224.7716	$224.77	$224.75	$224.80
Purchase #7	$68.90	4.777%	$72.1914	$72.19	$72.20	$72.20
7 purchase totals =	$584.11		$619.1411	$619.14	$619.10	$619.30