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	$44.46	13.803%	$50.5968	$50.60	$50.60	$50.60
Purchase #2	$232.84	12.529%	$262.0125	$262.01	$262.00	$262.00
Purchase #3	$158.38	11.483%	$176.5668	$176.57	$176.55	$176.60
Purchase #4	$174.61	12.606%	$196.6213	$196.62	$196.60	$196.60
Purchase #5	$104.81	12.631%	$118.0486	$118.05	$118.05	$118.00
Purchase #6	$61.42	3.140%	$63.3486	$63.35	$63.35	$63.30
Purchase #7	$137.32	4.635%	$143.6848	$143.68	$143.70	$143.70
7 purchase totals =	$913.84		$1,010.8794	$1,010.88	$1,010.85	$1,010.80