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	$144.39	13.604%	$164.0328	$164.03	$164.05	$164.00
Purchase #2	$21.33	6.791%	$22.7785	$22.78	$22.80	$22.80
Purchase #3	$115.47	9.463%	$126.3969	$126.40	$126.40	$126.40
Purchase #4	$135.45	9.563%	$148.4031	$148.40	$148.40	$148.40
Purchase #5	$208.72	5.242%	$219.6611	$219.66	$219.65	$219.70
Purchase #6	$89.34	12.773%	$100.7514	$100.75	$100.75	$100.80
Purchase #7	$73.86	3.639%	$76.5478	$76.55	$76.55	$76.50
7 purchase totals =	$788.56		$858.5716	$858.57	$858.60	$858.60