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	$205.71	8.646%	$223.4957	$223.50	$223.50	$223.50
Purchase #2	$217.37	12.806%	$245.2064	$245.21	$245.20	$245.20
Purchase #3	$100.55	10.798%	$111.4074	$111.41	$111.40	$111.40
Purchase #4	$230.36	10.688%	$254.9809	$254.98	$255.00	$255.00
Purchase #5	$49.73	9.577%	$54.4926	$54.49	$54.50	$54.50
Purchase #6	$30.68	4.582%	$32.0858	$32.09	$32.10	$32.10
Purchase #7	$196.88	9.683%	$215.9439	$215.94	$215.95	$215.90
7 purchase totals =	$1,031.28		$1,137.6127	$1,137.62	$1,137.65	$1,137.60