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	$77.54	5.255%	$81.6147	$81.61	$81.60	$81.60
Purchase #2	$9.29	13.478%	$10.5421	$10.54	$10.55	$10.50
Purchase #3	$221.94	10.435%	$245.0994	$245.10	$245.10	$245.10
Purchase #4	$13.42	12.751%	$15.1312	$15.13	$15.15	$15.10
Purchase #5	$205.88	5.632%	$217.4752	$217.48	$217.50	$217.50
Purchase #6	$198.93	11.298%	$221.4051	$221.41	$221.40	$221.40
Purchase #7	$94.32	6.599%	$100.5442	$100.54	$100.55	$100.50
7 purchase totals =	$821.32		$891.8119	$891.81	$891.85	$891.70