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	$168.40	9.320%	$184.0949	$184.09	$184.10	$184.10
Purchase #2	$169.88	12.399%	$190.9434	$190.94	$190.95	$190.90
Purchase #3	$114.73	8.447%	$124.4212	$124.42	$124.40	$124.40
Purchase #4	$227.61	9.218%	$248.5911	$248.59	$248.60	$248.60
Purchase #5	$128.40	4.717%	$134.4566	$134.46	$134.45	$134.50
Purchase #6	$117.76	12.517%	$132.5	$132.50	$132.50	$132.50
Purchase #7	$46.81	13.189%	$52.9838	$52.98	$53.00	$53.00
7 purchase totals =	$973.59		$1,067.9910	$1,067.98	$1,068.00	$1,068.00