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	$100.84	10.635%	$111.5643	$111.56	$111.55	$111.60
Purchase #2	$54.63	3.443%	$56.5109	$56.51	$56.50	$56.50
Purchase #3	$96.73	13.254%	$109.5506	$109.55	$109.55	$109.60
Purchase #4	$153.53	5.211%	$161.5304	$161.53	$161.55	$161.50
Purchase #5	$34.44	12.500%	$38.745	$38.75	$38.75	$38.70
Purchase #6	$46.47	11.109%	$51.6324	$51.63	$51.65	$51.60
Purchase #7	$169.93	6.829%	$181.5345	$181.53	$181.55	$181.50
7 purchase totals =	$656.57		$711.0681	$711.06	$711.10	$711.00