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	$239.39	12.727%	$269.8572	$269.86	$269.85	$269.90
Purchase #2	$134.72	12.466%	$151.5142	$151.51	$151.50	$151.50
Purchase #3	$75.67	6.331%	$80.4607	$80.46	$80.45	$80.50
Purchase #4	$222.43	6.533%	$236.9614	$236.96	$236.95	$237.00
Purchase #5	$35.55	8.509%	$38.5749	$38.57	$38.55	$38.60
Purchase #6	$91.95	9.161%	$100.3735	$100.37	$100.35	$100.40
Purchase #7	$140.33	11.693%	$156.7388	$156.74	$156.75	$156.70
7 purchase totals =	$940.04		$1,034.4807	$1,034.47	$1,034.40	$1,034.60