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	$152.94	12.619%	$172.2395	$172.24	$172.25	$172.20
Purchase #2	$241.65	11.557%	$269.5775	$269.58	$269.60	$269.60
Purchase #3	$137.51	12.756%	$155.0508	$155.05	$155.05	$155.10
Purchase #4	$133.43	7.610%	$143.584	$143.58	$143.60	$143.60
Purchase #5	$81.82	4.260%	$85.3055	$85.31	$85.30	$85.30
Purchase #6	$159.79	5.317%	$168.286	$168.29	$168.30	$168.30
Purchase #7	$21.25	12.534%	$23.9135	$23.91	$23.90	$23.90
7 purchase totals =	$928.39		$1,017.9568	$1,017.96	$1,018.00	$1,018.00