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	$12.68	10.248%	$13.9794	$13.98	$14.00	$14.00
Purchase #2	$141.78	11.804%	$158.5157	$158.52	$158.50	$158.50
Purchase #3	$233.70	10.453%	$258.1287	$258.13	$258.15	$258.10
Purchase #4	$192.27	4.762%	$201.4259	$201.43	$201.45	$201.40
Purchase #5	$105.82	5.751%	$111.9057	$111.91	$111.90	$111.90
Purchase #6	$150.35	3.865%	$156.161	$156.16	$156.15	$156.20
Purchase #7	$50.61	7.531%	$54.4214	$54.42	$54.40	$54.40
7 purchase totals =	$887.21		$954.5378	$954.55	$954.55	$954.50