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	$152.35	10.402%	$168.1974	$168.20	$168.20	$168.20
Purchase #2	$228.89	12.284%	$257.0068	$257.01	$257.00	$257.00
Purchase #3	$21.75	4.683%	$22.7686	$22.77	$22.75	$22.80
Purchase #4	$55.65	7.461%	$59.802	$59.80	$59.80	$59.80
Purchase #5	$150.33	9.286%	$164.2896	$164.29	$164.30	$164.30
Purchase #6	$182.52	9.507%	$199.8722	$199.87	$199.85	$199.90
Purchase #7	$10.78	6.785%	$11.5114	$11.51	$11.50	$11.50
7 purchase totals =	$802.27		$883.4480	$883.45	$883.40	$883.50