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	$217.46	9.359%	$237.8121	$237.81	$237.80	$237.80
Purchase #2	$206.51	7.838%	$222.6963	$222.70	$222.70	$222.70
Purchase #3	$225.36	13.310%	$255.3554	$255.36	$255.35	$255.40
Purchase #4	$108.96	13.691%	$123.8777	$123.88	$123.90	$123.90
Purchase #5	$204.70	12.548%	$230.3858	$230.39	$230.40	$230.40
Purchase #6	$105.94	7.548%	$113.9364	$113.94	$113.95	$113.90
Purchase #7	$64.96	9.217%	$70.9474	$70.95	$70.95	$70.90
7 purchase totals =	$1,133.89		$1,255.0111	$1,255.03	$1,255.05	$1,255.00