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	$96.45	4.195%	$100.4961	$100.50	$100.50	$100.50
Purchase #2	$21.39	7.187%	$22.9273	$22.93	$22.95	$22.90
Purchase #3	$160.98	5.285%	$169.4878	$169.49	$169.50	$169.50
Purchase #4	$169.85	5.107%	$178.5242	$178.52	$178.50	$178.50
Purchase #5	$107.46	10.217%	$118.4392	$118.44	$118.45	$118.40
Purchase #6	$115.25	7.116%	$123.4512	$123.45	$123.45	$123.50
Purchase #7	$23.64	5.488%	$24.9374	$24.94	$24.95	$24.90
7 purchase totals =	$695.02		$738.2632	$738.27	$738.30	$738.20