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	$116.92	5.414%	$123.25	$123.25	$123.25	$123.30
Purchase #2	$28.43	3.510%	$29.4279	$29.43	$29.45	$29.40
Purchase #3	$156.78	13.195%	$177.4671	$177.47	$177.45	$177.50
Purchase #4	$39.85	7.724%	$42.928	$42.93	$42.95	$42.90
Purchase #5	$142.53	13.261%	$161.4309	$161.43	$161.45	$161.40
Purchase #6	$113.42	8.736%	$123.3284	$123.33	$123.35	$123.30
Purchase #7	$171.95	12.712%	$193.8083	$193.81	$193.80	$193.80
7 purchase totals =	$769.88		$851.6406	$851.65	$851.70	$851.60