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	$50.65	8.451%	$54.9304	$54.93	$54.95	$54.90
Purchase #2	$59.56	11.222%	$66.2438	$66.24	$66.25	$66.20
Purchase #3	$184.61	6.278%	$196.1998	$196.20	$196.20	$196.20
Purchase #4	$28.85	10.205%	$31.7941	$31.79	$31.80	$31.80
Purchase #5	$145.94	3.782%	$151.4595	$151.46	$151.45	$151.50
Purchase #6	$8.94	11.283%	$9.9487	$9.95	$9.95	$9.90
Purchase #7	$194.28	5.727%	$205.4064	$205.41	$205.40	$205.40
7 purchase totals =	$672.83		$715.9827	$715.98	$716.00	$715.90