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	$125.32	13.838%	$142.6618	$142.66	$142.65	$142.70
Purchase #2	$166.64	4.382%	$173.9422	$173.94	$173.95	$173.90
Purchase #3	$176.44	4.855%	$185.0062	$185.01	$185.00	$185.00
Purchase #4	$36.26	4.202%	$37.7836	$37.78	$37.80	$37.80
Purchase #5	$153.98	6.222%	$163.5606	$163.56	$163.55	$163.60
Purchase #6	$57.69	3.793%	$59.8782	$59.88	$59.90	$59.90
Purchase #7	$88.54	13.456%	$100.4539	$100.45	$100.45	$100.50
7 purchase totals =	$804.87		$863.2865	$863.28	$863.30	$863.40