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	$128.50	12.699%	$144.8182	$144.82	$144.80	$144.80
Purchase #2	$95.53	5.225%	$100.5214	$100.52	$100.50	$100.50
Purchase #3	$45.84	5.807%	$48.5019	$48.50	$48.50	$48.50
Purchase #4	$21.47	5.179%	$22.5819	$22.58	$22.60	$22.60
Purchase #5	$16.45	12.117%	$18.4432	$18.44	$18.45	$18.40
Purchase #6	$127.71	6.795%	$136.3879	$136.39	$136.40	$136.40
Purchase #7	$193.38	10.674%	$214.0214	$214.02	$214.00	$214.00
7 purchase totals =	$628.88		$685.2759	$685.27	$685.25	$685.20