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	$237.59	3.593%	$246.1266	$246.13	$246.15	$246.10
Purchase #2	$242.88	3.208%	$250.6716	$250.67	$250.65	$250.70
Purchase #3	$20.42	6.396%	$21.7261	$21.73	$21.75	$21.70
Purchase #4	$29.42	5.393%	$31.0066	$31.01	$31.00	$31.00
Purchase #5	$62.43	9.135%	$68.133	$68.13	$68.15	$68.10
Purchase #6	$113.69	12.486%	$127.8853	$127.89	$127.90	$127.90
Purchase #7	$100.61	3.397%	$104.0277	$104.03	$104.05	$104.00
7 purchase totals =	$807.04		$849.5769	$849.59	$849.65	$849.50