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	$234.77	9.291%	$256.5825	$256.58	$256.60	$256.60
Purchase #2	$76.28	13.142%	$86.3047	$86.30	$86.30	$86.30
Purchase #3	$123.83	12.765%	$139.6369	$139.64	$139.65	$139.60
Purchase #4	$150.30	4.251%	$156.6893	$156.69	$156.70	$156.70
Purchase #5	$39.25	9.252%	$42.8814	$42.88	$42.90	$42.90
Purchase #6	$195.57	9.738%	$214.6146	$214.61	$214.60	$214.60
Purchase #7	$121.83	5.296%	$128.2821	$128.28	$128.30	$128.30
7 purchase totals =	$941.83		$1,024.9915	$1,024.98	$1,025.05	$1,025.00