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	$77.71	7.857%	$83.8157	$83.82	$83.80	$83.80
Purchase #2	$199.95	10.310%	$220.5648	$220.56	$220.55	$220.60
Purchase #3	$39.80	13.679%	$45.2442	$45.24	$45.25	$45.20
Purchase #4	$140.80	3.851%	$146.2222	$146.22	$146.20	$146.20
Purchase #5	$48.87	13.191%	$55.3164	$55.32	$55.30	$55.30
Purchase #6	$217.92	10.855%	$241.5752	$241.58	$241.60	$241.60
Purchase #7	$104.60	7.530%	$112.4764	$112.48	$112.50	$112.50
7 purchase totals =	$829.65		$905.2149	$905.22	$905.20	$905.20