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	$224.52	6.831%	$239.857	$239.86	$239.85	$239.90
Purchase #2	$6.78	6.693%	$7.2338	$7.23	$7.25	$7.20
Purchase #3	$223.28	11.560%	$249.0912	$249.09	$249.10	$249.10
Purchase #4	$106.67	4.151%	$111.0979	$111.10	$111.10	$111.10
Purchase #5	$173.94	10.134%	$191.5671	$191.57	$191.55	$191.60
Purchase #6	$187.42	11.506%	$208.9845	$208.98	$209.00	$209.00
Purchase #7	$83.59	5.734%	$88.3831	$88.38	$88.40	$88.40
7 purchase totals =	$1,006.20		$1,096.2146	$1,096.21	$1,096.25	$1,096.30