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	$112.56	12.867%	$127.0431	$127.04	$127.05	$127.00
Purchase #2	$116.94	11.693%	$130.6138	$130.61	$130.60	$130.60
Purchase #3	$9.46	11.679%	$10.5648	$10.56	$10.55	$10.60
Purchase #4	$83.65	6.680%	$89.2378	$89.24	$89.25	$89.20
Purchase #5	$139.39	3.126%	$143.7473	$143.75	$143.75	$143.70
Purchase #6	$190.34	7.825%	$205.2341	$205.23	$205.25	$205.20
Purchase #7	$104.56	9.664%	$114.6647	$114.66	$114.65	$114.70
7 purchase totals =	$756.90		$821.1056	$821.09	$821.10	$821.00