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	$42.27	8.104%	$45.6956	$45.70	$45.70	$45.70
Purchase #2	$40.41	10.660%	$44.7177	$44.72	$44.70	$44.70
Purchase #3	$136.70	4.856%	$143.3382	$143.34	$143.35	$143.30
Purchase #4	$27.51	13.590%	$31.2486	$31.25	$31.25	$31.20
Purchase #5	$41.55	10.163%	$45.7727	$45.77	$45.75	$45.80
Purchase #6	$84.65	13.311%	$95.9178	$95.92	$95.90	$95.90
Purchase #7	$71.44	8.510%	$77.5195	$77.52	$77.50	$77.50
7 purchase totals =	$444.53		$484.2101	$484.22	$484.15	$484.10