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	$152.90	10.247%	$168.5677	$168.57	$168.55	$168.60
Purchase #2	$95.52	5.114%	$100.4049	$100.40	$100.40	$100.40
Purchase #3	$249.38	3.317%	$257.6519	$257.65	$257.65	$257.70
Purchase #4	$241.47	11.757%	$269.8596	$269.86	$269.85	$269.90
Purchase #5	$167.39	11.477%	$186.6014	$186.60	$186.60	$186.60
Purchase #6	$160.66	7.465%	$172.6533	$172.65	$172.65	$172.70
Purchase #7	$95.49	6.733%	$101.9193	$101.92	$101.90	$101.90
7 purchase totals =	$1,162.81		$1,257.6581	$1,257.65	$1,257.60	$1,257.80