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	$98.96	9.725%	$108.5839	$108.58	$108.60	$108.60
Purchase #2	$137.57	5.476%	$145.1033	$145.10	$145.10	$145.10
Purchase #3	$38.78	11.149%	$43.1036	$43.10	$43.10	$43.10
Purchase #4	$90.99	3.862%	$94.504	$94.50	$94.50	$94.50
Purchase #5	$165.36	10.836%	$183.2784	$183.28	$183.30	$183.30
Purchase #6	$10.57	11.808%	$11.8181	$11.82	$11.80	$11.80
Purchase #7	$193.34	3.704%	$200.5013	$200.50	$200.50	$200.50
7 purchase totals =	$735.57		$786.8926	$786.88	$786.90	$786.90