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	$238.35	7.654%	$256.5933	$256.59	$256.60	$256.60
Purchase #2	$104.84	10.778%	$116.1397	$116.14	$116.15	$116.10
Purchase #3	$123.41	9.619%	$135.2808	$135.28	$135.30	$135.30
Purchase #4	$221.35	8.630%	$240.4525	$240.45	$240.45	$240.50
Purchase #5	$96.27	3.838%	$99.9648	$99.96	$99.95	$100.00
Purchase #6	$22.55	13.569%	$25.6098	$25.61	$25.60	$25.60
Purchase #7	$167.85	4.540%	$175.4704	$175.47	$175.45	$175.50
7 purchase totals =	$974.62		$1,049.5113	$1,049.50	$1,049.50	$1,049.60