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	$237.34	13.597%	$269.6111	$269.61	$269.60	$269.60
Purchase #2	$48.81	5.281%	$51.3877	$51.39	$51.40	$51.40
Purchase #3	$75.97	10.522%	$83.9636	$83.96	$83.95	$84.00
Purchase #4	$105.91	9.126%	$115.5753	$115.58	$115.60	$115.60
Purchase #5	$132.32	4.151%	$137.8126	$137.81	$137.80	$137.80
Purchase #6	$94.90	5.395%	$100.0199	$100.02	$100.00	$100.00
Purchase #7	$122.91	3.375%	$127.0582	$127.06	$127.05	$127.10
7 purchase totals =	$818.16		$885.4284	$885.43	$885.40	$885.50