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	$194.46	9.330%	$212.6031	$212.60	$212.60	$212.60
Purchase #2	$127.85	12.311%	$143.5896	$143.59	$143.60	$143.60
Purchase #3	$51.38	4.311%	$53.595	$53.60	$53.60	$53.60
Purchase #4	$188.61	5.461%	$198.91	$198.91	$198.90	$198.90
Purchase #5	$52.27	7.790%	$56.3418	$56.34	$56.35	$56.30
Purchase #6	$66.43	8.510%	$72.0832	$72.08	$72.10	$72.10
Purchase #7	$225.71	9.426%	$246.9854	$246.99	$247.00	$247.00
7 purchase totals =	$906.71		$984.1081	$984.11	$984.15	$984.10