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	$60.59	11.338%	$67.4597	$67.46	$67.45	$67.50
Purchase #2	$22.55	13.581%	$25.6125	$25.61	$25.60	$25.60
Purchase #3	$40.55	3.782%	$42.0836	$42.08	$42.10	$42.10
Purchase #4	$112.29	12.483%	$126.3072	$126.31	$126.30	$126.30
Purchase #5	$91.31	7.835%	$98.4641	$98.46	$98.45	$98.50
Purchase #6	$122.29	9.548%	$133.9662	$133.97	$133.95	$134.00
Purchase #7	$242.38	5.551%	$255.8345	$255.83	$255.85	$255.80
7 purchase totals =	$691.96		$749.7278	$749.72	$749.70	$749.80