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	$169.32	13.313%	$191.8616	$191.86	$191.85	$191.90
Purchase #2	$188.87	3.794%	$196.0357	$196.04	$196.05	$196.00
Purchase #3	$201.30	13.174%	$227.8193	$227.82	$227.80	$227.80
Purchase #4	$136.54	13.242%	$154.6206	$154.62	$154.60	$154.60
Purchase #5	$219.37	10.389%	$242.1603	$242.16	$242.15	$242.20
Purchase #6	$9.68	3.710%	$10.0391	$10.04	$10.05	$10.00
Purchase #7	$220.80	4.379%	$230.4688	$230.47	$230.45	$230.50
7 purchase totals =	$1,145.88		$1,253.0054	$1,253.01	$1,252.95	$1,253.00