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	$54.44	8.454%	$59.0424	$59.04	$59.05	$59.00
Purchase #2	$9.42	11.576%	$10.5105	$10.51	$10.50	$10.50
Purchase #3	$41.64	5.197%	$43.804	$43.80	$43.80	$43.80
Purchase #4	$78.49	6.127%	$83.2991	$83.30	$83.30	$83.30
Purchase #5	$196.87	11.579%	$219.6656	$219.67	$219.65	$219.70
Purchase #6	$17.92	13.431%	$20.3268	$20.33	$20.35	$20.30
Purchase #7	$29.98	5.756%	$31.7056	$31.71	$31.70	$31.70
7 purchase totals =	$428.76		$468.3540	$468.36	$468.35	$468.30