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	$198.91	11.412%	$221.6096	$221.61	$221.60	$221.60
Purchase #2	$41.47	5.742%	$43.8512	$43.85	$43.85	$43.90
Purchase #3	$140.56	11.296%	$156.4377	$156.44	$156.45	$156.40
Purchase #4	$184.68	12.713%	$208.1584	$208.16	$208.15	$208.20
Purchase #5	$183.32	5.616%	$193.6153	$193.62	$193.60	$193.60
Purchase #6	$65.31	9.533%	$71.536	$71.54	$71.55	$71.50
Purchase #7	$84.56	7.733%	$91.099	$91.10	$91.10	$91.10
7 purchase totals =	$898.81		$986.3072	$986.32	$986.30	$986.30