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	$104.46	6.453%	$111.2008	$111.20	$111.20	$111.20
Purchase #2	$175.55	3.361%	$181.4502	$181.45	$181.45	$181.50
Purchase #3	$11.50	12.149%	$12.8971	$12.90	$12.90	$12.90
Purchase #4	$127.55	12.537%	$143.5409	$143.54	$143.55	$143.50
Purchase #5	$123.87	11.604%	$138.2439	$138.24	$138.25	$138.20
Purchase #6	$232.86	9.748%	$255.5592	$255.56	$255.55	$255.60
Purchase #7	$205.95	6.651%	$219.6477	$219.65	$219.65	$219.60
7 purchase totals =	$981.74		$1,062.5398	$1,062.54	$1,062.55	$1,062.50