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	$164.50	3.448%	$170.172	$170.17	$170.15	$170.20
Purchase #2	$213.80	4.166%	$222.7069	$222.71	$222.70	$222.70
Purchase #3	$206.81	10.538%	$228.6036	$228.60	$228.60	$228.60
Purchase #4	$162.59	10.606%	$179.8343	$179.83	$179.85	$179.80
Purchase #5	$16.41	7.590%	$17.6555	$17.66	$17.65	$17.70
Purchase #6	$40.71	11.850%	$45.5341	$45.53	$45.55	$45.50
Purchase #7	$86.51	9.757%	$94.9508	$94.95	$94.95	$95.00
7 purchase totals =	$891.33		$959.4572	$959.45	$959.45	$959.50