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	$202.57	5.600%	$213.9139	$213.91	$213.90	$213.90
Purchase #2	$231.45	10.403%	$255.5277	$255.53	$255.55	$255.50
Purchase #3	$68.94	13.867%	$78.4999	$78.50	$78.50	$78.50
Purchase #4	$94.62	13.833%	$107.7088	$107.71	$107.70	$107.70
Purchase #5	$227.69	13.495%	$258.4168	$258.42	$258.40	$258.40
Purchase #6	$168.31	13.204%	$190.5337	$190.53	$190.55	$190.50
Purchase #7	$137.27	3.190%	$141.6489	$141.65	$141.65	$141.60
7 purchase totals =	$1,130.85		$1,246.2497	$1,246.25	$1,246.25	$1,246.10