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	$61.43	5.548%	$64.8381	$64.84	$64.85	$64.80
Purchase #2	$46.81	10.292%	$51.6277	$51.63	$51.65	$51.60
Purchase #3	$182.98	7.444%	$196.601	$196.60	$196.60	$196.60
Purchase #4	$151.51	10.567%	$167.5201	$167.52	$167.50	$167.50
Purchase #5	$17.37	5.349%	$18.2991	$18.30	$18.30	$18.30
Purchase #6	$173.90	4.702%	$182.0768	$182.08	$182.10	$182.10
Purchase #7	$74.42	3.367%	$76.9257	$76.93	$76.95	$76.90
7 purchase totals =	$708.42		$757.8885	$757.90	$757.95	$757.80