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	$158.88	4.583%	$166.1615	$166.16	$166.15	$166.20
Purchase #2	$49.87	3.436%	$51.5835	$51.58	$51.60	$51.60
Purchase #3	$100.84	10.173%	$111.0985	$111.10	$111.10	$111.10
Purchase #4	$226.86	4.306%	$236.6286	$236.63	$236.65	$236.60
Purchase #5	$102.77	13.120%	$116.2534	$116.25	$116.25	$116.30
Purchase #6	$66.57	8.165%	$72.0054	$72.01	$72.00	$72.00
Purchase #7	$191.82	11.443%	$213.77	$213.77	$213.75	$213.80
7 purchase totals =	$897.61		$967.5009	$967.50	$967.50	$967.60