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	$234.43	9.438%	$256.5555	$256.56	$256.55	$256.60
Purchase #2	$14.53	7.366%	$15.6003	$15.60	$15.60	$15.60
Purchase #3	$95.84	3.819%	$99.5001	$99.50	$99.50	$99.50
Purchase #4	$128.72	11.319%	$143.2898	$143.29	$143.30	$143.30
Purchase #5	$231.25	4.247%	$241.0712	$241.07	$241.05	$241.10
Purchase #6	$152.30	8.538%	$165.3034	$165.30	$165.30	$165.30
Purchase #7	$79.41	9.545%	$86.9897	$86.99	$87.00	$87.00
7 purchase totals =	$936.48		$1,008.3100	$1,008.31	$1,008.30	$1,008.40