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	$204.54	5.244%	$215.2661	$215.27	$215.25	$215.30
Purchase #2	$151.66	13.329%	$171.8748	$171.87	$171.85	$171.90
Purchase #3	$200.68	9.201%	$219.1446	$219.14	$219.15	$219.10
Purchase #4	$93.31	5.508%	$98.4495	$98.45	$98.45	$98.40
Purchase #5	$160.50	5.177%	$168.8091	$168.81	$168.80	$168.80
Purchase #6	$35.35	10.528%	$39.0716	$39.07	$39.05	$39.10
Purchase #7	$18.39	10.824%	$20.3805	$20.38	$20.40	$20.40
7 purchase totals =	$864.43		$932.9962	$932.99	$932.95	$933.00