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	$88.27	8.214%	$95.5205	$95.52	$95.50	$95.50
Purchase #2	$139.44	11.379%	$155.3069	$155.31	$155.30	$155.30
Purchase #3	$147.36	13.566%	$167.3509	$167.35	$167.35	$167.40
Purchase #4	$68.93	6.176%	$73.1871	$73.19	$73.20	$73.20
Purchase #5	$124.60	13.509%	$141.4322	$141.43	$141.45	$141.40
Purchase #6	$120.57	5.538%	$127.2472	$127.25	$127.25	$127.20
Purchase #7	$231.75	11.600%	$258.633	$258.63	$258.65	$258.60
7 purchase totals =	$920.92		$1,018.6778	$1,018.68	$1,018.70	$1,018.60