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	$222.57	6.810%	$237.727	$237.73	$237.75	$237.70
Purchase #2	$44.72	3.243%	$46.1703	$46.17	$46.15	$46.20
Purchase #3	$75.78	3.501%	$78.4331	$78.43	$78.45	$78.40
Purchase #4	$38.27	10.535%	$42.3017	$42.30	$42.30	$42.30
Purchase #5	$203.47	5.672%	$215.0108	$215.01	$215.00	$215.00
Purchase #6	$57.67	6.162%	$61.2236	$61.22	$61.20	$61.20
Purchase #7	$72.56	8.422%	$78.671	$78.67	$78.65	$78.70
7 purchase totals =	$715.04		$759.5375	$759.53	$759.50	$759.50