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	$108.42	3.138%	$111.8222	$111.82	$111.80	$111.80
Purchase #2	$205.57	11.405%	$229.0153	$229.02	$229.00	$229.00
Purchase #3	$55.63	11.313%	$61.9234	$61.92	$61.90	$61.90
Purchase #4	$233.88	3.271%	$241.5302	$241.53	$241.55	$241.50
Purchase #5	$51.46	13.235%	$58.2707	$58.27	$58.25	$58.30
Purchase #6	$236.25	8.143%	$255.4878	$255.49	$255.50	$255.50
Purchase #7	$52.47	8.492%	$56.9258	$56.93	$56.95	$56.90
7 purchase totals =	$943.68		$1,014.9754	$1,014.98	$1,014.95	$1,014.90