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	$218.82	10.462%	$241.7129	$241.71	$241.70	$241.70
Purchase #2	$238.96	7.129%	$255.9955	$256.00	$256.00	$256.00
Purchase #3	$122.97	11.750%	$137.419	$137.42	$137.40	$137.40
Purchase #4	$191.95	13.512%	$217.8863	$217.89	$217.90	$217.90
Purchase #5	$238.78	13.536%	$271.1013	$271.10	$271.10	$271.10
Purchase #6	$110.31	8.598%	$119.7945	$119.79	$119.80	$119.80
Purchase #7	$175.73	5.676%	$185.7044	$185.70	$185.70	$185.70
7 purchase totals =	$1,297.52		$1,429.6139	$1,429.61	$1,429.60	$1,429.60