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	$89.94	5.105%	$94.5314	$94.53	$94.55	$94.50
Purchase #2	$101.53	3.201%	$104.78	$104.78	$104.80	$104.80
Purchase #3	$249.32	3.849%	$258.9163	$258.92	$258.90	$258.90
Purchase #4	$204.40	6.202%	$217.0769	$217.08	$217.10	$217.10
Purchase #5	$90.53	9.517%	$99.1457	$99.15	$99.15	$99.10
Purchase #6	$108.42	12.163%	$121.6071	$121.61	$121.60	$121.60
Purchase #7	$210.53	12.487%	$236.8189	$236.82	$236.80	$236.80
7 purchase totals =	$1,054.67		$1,132.8763	$1,132.89	$1,132.90	$1,132.80