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	$227.90	12.464%	$256.3055	$256.31	$256.30	$256.30
Purchase #2	$51.68	11.528%	$57.6377	$57.64	$57.65	$57.60
Purchase #3	$10.64	3.794%	$11.0437	$11.04	$11.05	$11.00
Purchase #4	$141.92	7.867%	$153.0848	$153.08	$153.10	$153.10
Purchase #5	$185.82	3.872%	$193.015	$193.02	$193.00	$193.00
Purchase #6	$231.78	10.174%	$255.3613	$255.36	$255.35	$255.40
Purchase #7	$99.88	11.454%	$111.3203	$111.32	$111.30	$111.30
7 purchase totals =	$949.62		$1,037.7683	$1,037.77	$1,037.75	$1,037.70