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	$120.30	13.430%	$136.4563	$136.46	$136.45	$136.50
Purchase #2	$177.43	10.626%	$196.2837	$196.28	$196.30	$196.30
Purchase #3	$100.32	5.477%	$105.8145	$105.81	$105.80	$105.80
Purchase #4	$176.38	13.502%	$200.1948	$200.19	$200.20	$200.20
Purchase #5	$158.47	10.680%	$175.3946	$175.39	$175.40	$175.40
Purchase #6	$150.96	5.127%	$158.6997	$158.70	$158.70	$158.70
Purchase #7	$8.43	5.147%	$8.8639	$8.86	$8.85	$8.90
7 purchase totals =	$892.29		$981.7075	$981.69	$981.70	$981.80