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	$238.81	11.345%	$265.903	$265.90	$265.90	$265.90
Purchase #2	$53.90	4.574%	$56.3654	$56.37	$56.35	$56.40
Purchase #3	$50.37	4.184%	$52.4775	$52.48	$52.50	$52.50
Purchase #4	$31.87	4.497%	$33.3032	$33.30	$33.30	$33.30
Purchase #5	$5.78	7.445%	$6.2103	$6.21	$6.20	$6.20
Purchase #6	$129.93	10.451%	$143.509	$143.51	$143.50	$143.50
Purchase #7	$127.71	12.491%	$143.6623	$143.66	$143.65	$143.70
7 purchase totals =	$638.37		$701.4307	$701.43	$701.40	$701.50