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	$38.86	9.434%	$42.5261	$42.53	$42.55	$42.50
Purchase #2	$89.50	3.341%	$92.4902	$92.49	$92.50	$92.50
Purchase #3	$155.52	5.720%	$164.4157	$164.42	$164.40	$164.40
Purchase #4	$146.63	12.166%	$164.469	$164.47	$164.45	$164.50
Purchase #5	$42.69	7.748%	$45.9976	$46.00	$46.00	$46.00
Purchase #6	$30.53	10.784%	$33.8224	$33.82	$33.80	$33.80
Purchase #7	$150.51	9.201%	$164.3584	$164.36	$164.35	$164.40
7 purchase totals =	$654.24		$708.0794	$708.09	$708.05	$708.10