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	$212.81	3.456%	$220.1647	$220.16	$220.15	$220.20
Purchase #2	$248.57	11.393%	$276.8896	$276.89	$276.90	$276.90
Purchase #3	$163.27	4.835%	$171.1641	$171.16	$171.15	$171.20
Purchase #4	$65.31	8.547%	$70.892	$70.89	$70.90	$70.90
Purchase #5	$100.62	10.549%	$111.2344	$111.23	$111.25	$111.20
Purchase #6	$98.79	6.712%	$105.4208	$105.42	$105.40	$105.40
Purchase #7	$59.62	5.201%	$62.7208	$62.72	$62.70	$62.70
7 purchase totals =	$948.99		$1,018.4864	$1,018.47	$1,018.45	$1,018.50