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	$96.30	4.387%	$100.5247	$100.52	$100.50	$100.50
Purchase #2	$40.68	12.841%	$45.9037	$45.90	$45.90	$45.90
Purchase #3	$168.55	7.407%	$181.0345	$181.03	$181.05	$181.00
Purchase #4	$228.92	11.629%	$255.5411	$255.54	$255.55	$255.50
Purchase #5	$34.62	6.789%	$36.9704	$36.97	$36.95	$37.00
Purchase #6	$221.77	11.361%	$246.9653	$246.97	$246.95	$247.00
Purchase #7	$171.40	10.652%	$189.6575	$189.66	$189.65	$189.70
7 purchase totals =	$962.24		$1,056.5972	$1,056.59	$1,056.55	$1,056.60