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	$42.94	5.371%	$45.2463	$45.25	$45.25	$45.20
Purchase #2	$216.93	11.493%	$241.8618	$241.86	$241.85	$241.90
Purchase #3	$38.60	5.788%	$40.8342	$40.83	$40.85	$40.80
Purchase #4	$17.50	5.436%	$18.4513	$18.45	$18.45	$18.50
Purchase #5	$174.25	9.170%	$190.2287	$190.23	$190.25	$190.20
Purchase #6	$17.49	9.166%	$19.0931	$19.09	$19.10	$19.10
Purchase #7	$161.97	10.695%	$179.2927	$179.29	$179.30	$179.30
7 purchase totals =	$669.68		$735.0081	$735.00	$735.05	$735.00