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	$74.25	11.705%	$82.941	$82.94	$82.95	$82.90
Purchase #2	$131.68	9.180%	$143.7682	$143.77	$143.75	$143.80
Purchase #3	$194.85	6.798%	$208.0959	$208.10	$208.10	$208.10
Purchase #4	$93.33	7.764%	$100.5761	$100.58	$100.60	$100.60
Purchase #5	$193.80	10.446%	$214.0443	$214.04	$214.05	$214.00
Purchase #6	$47.46	12.545%	$53.4139	$53.41	$53.40	$53.40
Purchase #7	$130.93	7.255%	$140.429	$140.43	$140.45	$140.40
7 purchase totals =	$866.30		$943.2684	$943.27	$943.30	$943.20