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	$167.35	6.624%	$178.4353	$178.44	$178.45	$178.40
Purchase #2	$182.34	9.624%	$199.8884	$199.89	$199.90	$199.90
Purchase #3	$68.69	5.849%	$72.7077	$72.71	$72.70	$72.70
Purchase #4	$174.86	7.453%	$187.8923	$187.89	$187.90	$187.90
Purchase #5	$124.80	7.792%	$134.5244	$134.52	$134.50	$134.50
Purchase #6	$126.54	10.296%	$139.5686	$139.57	$139.55	$139.60
Purchase #7	$122.47	3.605%	$126.885	$126.89	$126.90	$126.90
7 purchase totals =	$967.05		$1,039.9017	$1,039.91	$1,039.90	$1,039.90