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	$68.56	11.733%	$76.6041	$76.60	$76.60	$76.60
Purchase #2	$26.92	13.240%	$30.4842	$30.48	$30.50	$30.50
Purchase #3	$154.94	13.778%	$176.2876	$176.29	$176.30	$176.30
Purchase #4	$227.67	12.676%	$256.5294	$256.53	$256.55	$256.50
Purchase #5	$36.77	10.367%	$40.5819	$40.58	$40.60	$40.60
Purchase #6	$78.63	13.339%	$89.1185	$89.12	$89.10	$89.10
Purchase #7	$104.25	11.672%	$116.4181	$116.42	$116.40	$116.40
7 purchase totals =	$697.74		$786.0238	$786.02	$786.05	$786.00