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	$201.76	3.209%	$208.2345	$208.23	$208.25	$208.20
Purchase #2	$46.60	11.791%	$52.0946	$52.09	$52.10	$52.10
Purchase #3	$194.69	11.189%	$216.4739	$216.47	$216.45	$216.50
Purchase #4	$23.69	7.630%	$25.4975	$25.50	$25.50	$25.50
Purchase #5	$126.98	3.764%	$131.7595	$131.76	$131.75	$131.80
Purchase #6	$104.85	7.716%	$112.9402	$112.94	$112.95	$112.90
Purchase #7	$147.41	4.149%	$153.526	$153.53	$153.55	$153.50
7 purchase totals =	$845.98		$900.5262	$900.52	$900.55	$900.50