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	$193.51	6.247%	$205.5986	$205.60	$205.60	$205.60
Purchase #2	$56.85	4.342%	$59.3184	$59.32	$59.30	$59.30
Purchase #3	$154.69	9.587%	$169.5201	$169.52	$169.50	$169.50
Purchase #4	$195.86	7.733%	$211.0059	$211.01	$211.00	$211.00
Purchase #5	$250.97	7.530%	$269.868	$269.87	$269.85	$269.90
Purchase #6	$96.85	9.703%	$106.2474	$106.25	$106.25	$106.20
Purchase #7	$160.73	6.484%	$171.1517	$171.15	$171.15	$171.20
7 purchase totals =	$1,109.46		$1,192.7101	$1,192.72	$1,192.65	$1,192.70