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	$208.97	3.257%	$215.7762	$215.78	$215.80	$215.80
Purchase #2	$48.86	6.128%	$51.8541	$51.85	$51.85	$51.90
Purchase #3	$62.86	7.620%	$67.6499	$67.65	$67.65	$67.60
Purchase #4	$74.56	8.114%	$80.6098	$80.61	$80.60	$80.60
Purchase #5	$125.64	4.123%	$130.8201	$130.82	$130.80	$130.80
Purchase #6	$123.93	12.279%	$139.1474	$139.15	$139.15	$139.10
Purchase #7	$35.77	9.603%	$39.205	$39.21	$39.20	$39.20
7 purchase totals =	$680.59		$725.0625	$725.07	$725.05	$725.00