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	$183.94	6.708%	$196.2787	$196.28	$196.30	$196.30
Purchase #2	$137.80	4.601%	$144.1402	$144.14	$144.15	$144.10
Purchase #3	$143.73	11.390%	$160.1008	$160.10	$160.10	$160.10
Purchase #4	$56.28	9.819%	$61.8061	$61.81	$61.80	$61.80
Purchase #5	$43.42	5.181%	$45.6696	$45.67	$45.65	$45.70
Purchase #6	$103.86	13.189%	$117.5581	$117.56	$117.55	$117.60
Purchase #7	$222.61	8.713%	$242.006	$242.01	$242.00	$242.00
7 purchase totals =	$891.64		$967.5595	$967.57	$967.55	$967.60