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	$20.98	10.113%	$23.1017	$23.10	$23.10	$23.10
Purchase #2	$238.67	11.633%	$266.4345	$266.43	$266.45	$266.40
Purchase #3	$65.55	10.547%	$72.4636	$72.46	$72.45	$72.50
Purchase #4	$189.82	5.694%	$200.6284	$200.63	$200.65	$200.60
Purchase #5	$50.55	4.407%	$52.7777	$52.78	$52.80	$52.80
Purchase #6	$208.52	3.150%	$215.0884	$215.09	$215.10	$215.10
Purchase #7	$232.80	10.564%	$257.393	$257.39	$257.40	$257.40
7 purchase totals =	$1,006.89		$1,087.8873	$1,087.88	$1,087.95	$1,087.90