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	$124.55	5.245%	$131.0826	$131.08	$131.10	$131.10
Purchase #2	$172.96	8.661%	$187.9401	$187.94	$187.95	$187.90
Purchase #3	$82.27	11.551%	$91.773	$91.77	$91.75	$91.80
Purchase #4	$161.74	13.763%	$184.0003	$184.00	$184.00	$184.00
Purchase #5	$177.96	12.638%	$200.4506	$200.45	$200.45	$200.50
Purchase #6	$200.66	11.433%	$223.6015	$223.60	$223.60	$223.60
Purchase #7	$132.53	5.305%	$139.5607	$139.56	$139.55	$139.60
7 purchase totals =	$1,052.67		$1,158.4088	$1,158.40	$1,158.40	$1,158.50