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	$174.29	4.688%	$182.4607	$182.46	$182.45	$182.50
Purchase #2	$239.46	12.704%	$269.881	$269.88	$269.90	$269.90
Purchase #3	$7.51	8.447%	$8.1444	$8.14	$8.15	$8.10
Purchase #4	$58.80	13.222%	$66.5745	$66.57	$66.55	$66.60
Purchase #5	$76.80	5.237%	$80.822	$80.82	$80.80	$80.80
Purchase #6	$126.56	13.647%	$143.8316	$143.83	$143.85	$143.80
Purchase #7	$101.80	9.794%	$111.7703	$111.77	$111.75	$111.80
7 purchase totals =	$785.22		$863.4845	$863.47	$863.45	$863.50