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	$175.91	8.201%	$190.3364	$190.34	$190.35	$190.30
Purchase #2	$76.95	7.153%	$82.4542	$82.45	$82.45	$82.50
Purchase #3	$206.65	13.813%	$235.1946	$235.19	$235.20	$235.20
Purchase #4	$69.25	13.108%	$78.3273	$78.33	$78.35	$78.30
Purchase #5	$12.89	4.833%	$13.513	$13.51	$13.50	$13.50
Purchase #6	$75.96	3.364%	$78.5153	$78.52	$78.50	$78.50
Purchase #7	$241.96	9.527%	$265.0115	$265.01	$265.00	$265.00
7 purchase totals =	$859.57		$943.3523	$943.35	$943.35	$943.30