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	$238.82	4.442%	$249.4284	$249.43	$249.45	$249.40
Purchase #2	$134.60	13.757%	$153.1169	$153.12	$153.10	$153.10
Purchase #3	$86.76	13.509%	$98.4804	$98.48	$98.50	$98.50
Purchase #4	$6.61	7.148%	$7.0825	$7.08	$7.10	$7.10
Purchase #5	$221.49	11.483%	$246.9237	$246.92	$246.90	$246.90
Purchase #6	$55.31	10.462%	$61.0965	$61.10	$61.10	$61.10
Purchase #7	$105.40	6.109%	$111.8389	$111.84	$111.85	$111.80
7 purchase totals =	$848.99		$927.9673	$927.97	$928.00	$927.90