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	$118.53	4.451%	$123.8058	$123.81	$123.80	$123.80
Purchase #2	$152.56	10.181%	$168.0921	$168.09	$168.10	$168.10
Purchase #3	$215.80	9.753%	$236.847	$236.85	$236.85	$236.80
Purchase #4	$74.89	5.836%	$79.2606	$79.26	$79.25	$79.30
Purchase #5	$159.42	3.150%	$164.4417	$164.44	$164.45	$164.40
Purchase #6	$62.29	10.426%	$68.7844	$68.78	$68.80	$68.80
Purchase #7	$63.34	5.787%	$67.0055	$67.01	$67.00	$67.00
7 purchase totals =	$846.83		$908.2371	$908.24	$908.25	$908.20