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	$119.48	3.162%	$123.258	$123.26	$123.25	$123.30
Purchase #2	$184.56	13.433%	$209.3519	$209.35	$209.35	$209.40
Purchase #3	$106.65	13.266%	$120.7982	$120.80	$120.80	$120.80
Purchase #4	$210.28	4.235%	$219.1854	$219.19	$219.20	$219.20
Purchase #5	$208.47	6.768%	$222.5792	$222.58	$222.60	$222.60
Purchase #6	$76.86	8.591%	$83.463	$83.46	$83.45	$83.50
Purchase #7	$64.35	3.240%	$66.4349	$66.43	$66.45	$66.40
7 purchase totals =	$970.65		$1,045.0706	$1,045.07	$1,045.10	$1,045.20