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	$42.31	7.697%	$45.5666	$45.57	$45.55	$45.60
Purchase #2	$117.65	6.125%	$124.8561	$124.86	$124.85	$124.90
Purchase #3	$116.60	5.709%	$123.2567	$123.26	$123.25	$123.30
Purchase #4	$192.32	6.747%	$205.2958	$205.30	$205.30	$205.30
Purchase #5	$51.68	10.541%	$57.1276	$57.13	$57.15	$57.10
Purchase #6	$80.51	13.556%	$91.4239	$91.42	$91.40	$91.40
Purchase #7	$59.83	11.167%	$66.5112	$66.51	$66.50	$66.50
7 purchase totals =	$660.90		$714.0379	$714.05	$714.00	$714.10