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	$104.54	12.738%	$117.8563	$117.86	$117.85	$117.90
Purchase #2	$169.95	8.753%	$184.8257	$184.83	$184.85	$184.80
Purchase #3	$78.61	12.139%	$88.1525	$88.15	$88.15	$88.20
Purchase #4	$126.82	10.857%	$140.5888	$140.59	$140.60	$140.60
Purchase #5	$128.95	3.328%	$133.2415	$133.24	$133.25	$133.20
Purchase #6	$236.87	10.733%	$262.2933	$262.29	$262.30	$262.30
Purchase #7	$125.96	10.724%	$139.468	$139.47	$139.45	$139.50
7 purchase totals =	$971.70		$1,066.4261	$1,066.43	$1,066.45	$1,066.50