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	$111.83	4.478%	$116.8377	$116.84	$116.85	$116.80
Purchase #2	$17.27	13.480%	$19.598	$19.60	$19.60	$19.60
Purchase #3	$62.25	3.661%	$64.529	$64.53	$64.55	$64.50
Purchase #4	$56.81	10.543%	$62.7995	$62.80	$62.80	$62.80
Purchase #5	$63.89	4.223%	$66.5881	$66.59	$66.60	$66.60
Purchase #6	$101.92	6.446%	$108.4898	$108.49	$108.50	$108.50
Purchase #7	$137.48	7.628%	$147.967	$147.97	$147.95	$148.00
7 purchase totals =	$551.45		$586.8091	$586.82	$586.85	$586.80