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	$54.91	8.564%	$59.6125	$59.61	$59.60	$59.60
Purchase #2	$143.80	9.143%	$156.9476	$156.95	$156.95	$156.90
Purchase #3	$179.56	3.624%	$186.0673	$186.07	$186.05	$186.10
Purchase #4	$66.53	13.134%	$75.2681	$75.27	$75.25	$75.30
Purchase #5	$134.82	12.509%	$151.6846	$151.68	$151.70	$151.70
Purchase #6	$83.86	12.238%	$94.1228	$94.12	$94.10	$94.10
Purchase #7	$154.64	10.859%	$171.4324	$171.43	$171.45	$171.40
7 purchase totals =	$818.12		$895.1353	$895.13	$895.10	$895.10