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	$68.40	6.165%	$72.6169	$72.62	$72.60	$72.60
Purchase #2	$249.38	3.811%	$258.8839	$258.88	$258.90	$258.90
Purchase #3	$111.77	8.280%	$121.0246	$121.02	$121.00	$121.00
Purchase #4	$120.51	6.344%	$128.1552	$128.16	$128.15	$128.20
Purchase #5	$163.85	5.214%	$172.3931	$172.39	$172.40	$172.40
Purchase #6	$78.94	13.397%	$89.5156	$89.52	$89.50	$89.50
Purchase #7	$169.89	12.663%	$191.4032	$191.40	$191.40	$191.40
7 purchase totals =	$962.74		$1,033.9925	$1,033.99	$1,033.95	$1,034.00