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	$46.47	7.301%	$49.8628	$49.86	$49.85	$49.90
Purchase #2	$205.85	6.297%	$218.8124	$218.81	$218.80	$218.80
Purchase #3	$213.85	13.497%	$242.7133	$242.71	$242.70	$242.70
Purchase #4	$27.52	8.213%	$29.7802	$29.78	$29.80	$29.80
Purchase #5	$99.57	6.354%	$105.8967	$105.90	$105.90	$105.90
Purchase #6	$248.78	7.592%	$267.6674	$267.67	$267.65	$267.70
Purchase #7	$12.85	10.105%	$14.1485	$14.15	$14.15	$14.10
7 purchase totals =	$854.89		$928.8813	$928.88	$928.85	$928.90