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	$151.74	8.509%	$164.6516	$164.65	$164.65	$164.70
Purchase #2	$132.67	6.145%	$140.8226	$140.82	$140.80	$140.80
Purchase #3	$136.60	4.303%	$142.4779	$142.48	$142.50	$142.50
Purchase #4	$169.67	6.435%	$180.5883	$180.59	$180.60	$180.60
Purchase #5	$199.55	5.643%	$210.8106	$210.81	$210.80	$210.80
Purchase #6	$209.86	11.217%	$233.4	$233.40	$233.40	$233.40
Purchase #7	$220.36	9.719%	$241.7768	$241.78	$241.80	$241.80
7 purchase totals =	$1,220.45		$1,314.5278	$1,314.53	$1,314.55	$1,314.60