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	$127.43	10.420%	$140.7082	$140.71	$140.70	$140.70
Purchase #2	$114.85	7.664%	$123.6521	$123.65	$123.65	$123.70
Purchase #3	$86.56	10.360%	$95.5276	$95.53	$95.55	$95.50
Purchase #4	$206.75	8.108%	$223.5133	$223.51	$223.50	$223.50
Purchase #5	$108.49	11.236%	$120.6799	$120.68	$120.70	$120.70
Purchase #6	$100.85	11.770%	$112.72	$112.72	$112.70	$112.70
Purchase #7	$219.60	6.109%	$233.0154	$233.02	$233.00	$233.00
7 purchase totals =	$964.53		$1,049.8165	$1,049.82	$1,049.80	$1,049.80