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	$191.59	12.176%	$214.918	$214.92	$214.90	$214.90
Purchase #2	$103.72	7.347%	$111.3403	$111.34	$111.35	$111.30
Purchase #3	$233.96	3.515%	$242.1837	$242.18	$242.20	$242.20
Purchase #4	$239.49	6.733%	$255.6149	$255.61	$255.60	$255.60
Purchase #5	$204.25	9.114%	$222.8653	$222.87	$222.85	$222.90
Purchase #6	$243.66	13.773%	$277.2193	$277.22	$277.20	$277.20
Purchase #7	$104.47	12.833%	$117.8766	$117.88	$117.90	$117.90
7 purchase totals =	$1,321.14		$1,442.0181	$1,442.02	$1,442.00	$1,442.00