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	$113.35	12.792%	$127.8497	$127.85	$127.85	$127.80
Purchase #2	$238.98	8.191%	$258.5549	$258.55	$258.55	$258.60
Purchase #3	$212.67	3.483%	$220.0773	$220.08	$220.10	$220.10
Purchase #4	$144.56	11.615%	$161.3506	$161.35	$161.35	$161.40
Purchase #5	$169.42	7.466%	$182.0689	$182.07	$182.05	$182.10
Purchase #6	$38.65	5.798%	$40.8909	$40.89	$40.90	$40.90
Purchase #7	$130.43	11.847%	$145.882	$145.88	$145.90	$145.90
7 purchase totals =	$1,048.06		$1,136.6743	$1,136.67	$1,136.70	$1,136.80