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	$63.71	10.672%	$70.5091	$70.51	$70.50	$70.50
Purchase #2	$48.31	7.441%	$51.9047	$51.90	$51.90	$51.90
Purchase #3	$206.54	6.338%	$219.6305	$219.63	$219.65	$219.60
Purchase #4	$127.42	11.675%	$142.2963	$142.30	$142.30	$142.30
Purchase #5	$89.56	6.418%	$95.308	$95.31	$95.30	$95.30
Purchase #6	$111.72	11.220%	$124.255	$124.26	$124.25	$124.30
Purchase #7	$237.98	7.137%	$254.9646	$254.96	$254.95	$255.00
7 purchase totals =	$885.24		$958.8682	$958.87	$958.85	$958.90