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	$227.94	5.849%	$241.2722	$241.27	$241.25	$241.30
Purchase #2	$72.79	13.195%	$82.3946	$82.39	$82.40	$82.40
Purchase #3	$127.84	9.858%	$140.4425	$140.44	$140.45	$140.40
Purchase #4	$116.81	12.756%	$131.7103	$131.71	$131.70	$131.70
Purchase #5	$118.90	3.130%	$122.6216	$122.62	$122.60	$122.60
Purchase #6	$82.98	3.213%	$85.6461	$85.65	$85.65	$85.60
Purchase #7	$132.63	6.476%	$141.2191	$141.22	$141.20	$141.20
7 purchase totals =	$879.89		$945.3064	$945.30	$945.25	$945.20