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	$230.98	10.763%	$255.8404	$255.84	$255.85	$255.80
Purchase #2	$221.73	10.545%	$245.1114	$245.11	$245.10	$245.10
Purchase #3	$166.27	7.108%	$178.0885	$178.09	$178.10	$178.10
Purchase #4	$182.26	4.735%	$190.89	$190.89	$190.90	$190.90
Purchase #5	$9.82	5.562%	$10.3662	$10.37	$10.35	$10.40
Purchase #6	$79.78	10.173%	$87.896	$87.90	$87.90	$87.90
Purchase #7	$222.98	6.210%	$236.8271	$236.83	$236.85	$236.80
7 purchase totals =	$1,113.82		$1,205.0196	$1,205.03	$1,205.05	$1,205.00