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	$165.45	4.167%	$172.3443	$172.34	$172.35	$172.30
Purchase #2	$80.94	8.451%	$87.7802	$87.78	$87.80	$87.80
Purchase #3	$141.64	10.713%	$156.8139	$156.81	$156.80	$156.80
Purchase #4	$140.32	11.485%	$156.4358	$156.44	$156.45	$156.40
Purchase #5	$13.47	13.329%	$15.2654	$15.27	$15.25	$15.30
Purchase #6	$219.71	6.870%	$234.8041	$234.80	$234.80	$234.80
Purchase #7	$210.72	5.592%	$222.5035	$222.50	$222.50	$222.50
7 purchase totals =	$972.25		$1,045.9472	$1,045.94	$1,045.95	$1,045.90