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	$37.42	10.580%	$41.379	$41.38	$41.40	$41.40
Purchase #2	$58.76	12.370%	$66.0286	$66.03	$66.05	$66.00
Purchase #3	$205.83	4.241%	$214.5593	$214.56	$214.55	$214.60
Purchase #4	$209.97	12.739%	$236.7181	$236.72	$236.70	$236.70
Purchase #5	$238.41	7.128%	$255.4039	$255.40	$255.40	$255.40
Purchase #6	$150.96	11.856%	$168.8578	$168.86	$168.85	$168.90
Purchase #7	$59.81	11.613%	$66.7557	$66.76	$66.75	$66.80
7 purchase totals =	$961.16		$1,049.7024	$1,049.71	$1,049.70	$1,049.80