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	$60.72	9.266%	$66.3463	$66.35	$66.35	$66.30
Purchase #2	$132.68	8.115%	$143.447	$143.45	$143.45	$143.40
Purchase #3	$21.69	5.118%	$22.8001	$22.80	$22.80	$22.80
Purchase #4	$185.54	3.460%	$191.9597	$191.96	$191.95	$192.00
Purchase #5	$56.49	5.870%	$59.806	$59.81	$59.80	$59.80
Purchase #6	$105.50	4.243%	$109.9764	$109.98	$110.00	$110.00
Purchase #7	$118.52	4.470%	$123.8178	$123.82	$123.80	$123.80
7 purchase totals =	$681.14		$718.1533	$718.17	$718.15	$718.10