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	$249.36	4.863%	$261.4864	$261.49	$261.50	$261.50
Purchase #2	$78.82	6.329%	$83.8085	$83.81	$83.80	$83.80
Purchase #3	$113.28	5.786%	$119.8344	$119.83	$119.85	$119.80
Purchase #4	$177.58	12.613%	$199.9782	$199.98	$200.00	$200.00
Purchase #5	$189.85	10.397%	$209.5887	$209.59	$209.60	$209.60
Purchase #6	$33.83	5.590%	$35.7211	$35.72	$35.70	$35.70
Purchase #7	$226.46	6.798%	$241.8548	$241.85	$241.85	$241.90
7 purchase totals =	$1,069.18		$1,152.2721	$1,152.27	$1,152.30	$1,152.30