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	$50.31	11.531%	$56.1112	$56.11	$56.10	$56.10
Purchase #2	$232.52	10.465%	$256.8532	$256.85	$256.85	$256.90
Purchase #3	$229.62	6.576%	$244.7198	$244.72	$244.70	$244.70
Purchase #4	$245.93	10.724%	$272.3035	$272.30	$272.30	$272.30
Purchase #5	$163.80	5.316%	$172.5076	$172.51	$172.50	$172.50
Purchase #6	$11.96	13.681%	$13.5962	$13.60	$13.60	$13.60
Purchase #7	$103.61	12.783%	$116.8545	$116.85	$116.85	$116.90
7 purchase totals =	$1,037.75		$1,132.9460	$1,132.94	$1,132.90	$1,133.00