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	$14.42	3.508%	$14.9259	$14.93	$14.95	$14.90
Purchase #2	$212.43	7.245%	$227.8206	$227.82	$227.80	$227.80
Purchase #3	$31.65	4.715%	$33.1423	$33.14	$33.15	$33.10
Purchase #4	$227.77	13.565%	$258.667	$258.67	$258.65	$258.70
Purchase #5	$29.80	8.165%	$32.2332	$32.23	$32.25	$32.20
Purchase #6	$139.81	10.475%	$154.4551	$154.46	$154.45	$154.50
Purchase #7	$108.98	3.256%	$112.5284	$112.53	$112.55	$112.50
7 purchase totals =	$764.86		$833.7725	$833.78	$833.80	$833.70