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	$199.44	7.373%	$214.1447	$214.14	$214.15	$214.10
Purchase #2	$190.88	4.699%	$199.8495	$199.85	$199.85	$199.80
Purchase #3	$43.92	8.523%	$47.6633	$47.66	$47.65	$47.70
Purchase #4	$38.42	5.523%	$40.5419	$40.54	$40.55	$40.50
Purchase #5	$99.72	11.799%	$111.486	$111.49	$111.50	$111.50
Purchase #6	$115.83	13.121%	$131.0281	$131.03	$131.05	$131.00
Purchase #7	$43.58	6.660%	$46.4824	$46.48	$46.50	$46.50
7 purchase totals =	$731.79		$791.1959	$791.19	$791.25	$791.10