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	$100.64	10.509%	$111.2163	$111.22	$111.20	$111.20
Purchase #2	$207.77	6.119%	$220.4834	$220.48	$220.50	$220.50
Purchase #3	$143.79	8.712%	$156.317	$156.32	$156.30	$156.30
Purchase #4	$160.38	9.660%	$175.8727	$175.87	$175.85	$175.90
Purchase #5	$189.96	13.404%	$215.4222	$215.42	$215.40	$215.40
Purchase #6	$52.33	5.193%	$55.0475	$55.05	$55.05	$55.00
Purchase #7	$131.76	5.589%	$139.1241	$139.12	$139.10	$139.10
7 purchase totals =	$986.63		$1,073.4832	$1,073.48	$1,073.40	$1,073.40