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	$76.68	10.241%	$84.5328	$84.53	$84.55	$84.50
Purchase #2	$20.60	3.756%	$21.3737	$21.37	$21.35	$21.40
Purchase #3	$57.25	12.547%	$64.4332	$64.43	$64.45	$64.40
Purchase #4	$212.89	4.522%	$222.5169	$222.52	$222.50	$222.50
Purchase #5	$177.56	9.469%	$194.3732	$194.37	$194.35	$194.40
Purchase #6	$224.82	5.765%	$237.7809	$237.78	$237.80	$237.80
Purchase #7	$136.50	4.685%	$142.895	$142.90	$142.90	$142.90
7 purchase totals =	$906.30		$967.9057	$967.90	$967.90	$967.90