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	$6.81	10.614%	$7.5328	$7.53	$7.55	$7.50
Purchase #2	$19.58	5.221%	$20.6023	$20.60	$20.60	$20.60
Purchase #3	$37.47	12.340%	$42.0938	$42.09	$42.10	$42.10
Purchase #4	$17.40	8.862%	$18.942	$18.94	$18.95	$18.90
Purchase #5	$231.60	10.123%	$255.0449	$255.04	$255.05	$255.00
Purchase #6	$179.95	12.208%	$201.9183	$201.92	$201.90	$201.90
Purchase #7	$181.98	7.741%	$196.0671	$196.07	$196.05	$196.10
7 purchase totals =	$674.79		$742.2012	$742.19	$742.20	$742.10