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	$16.94	4.307%	$17.6696	$17.67	$17.65	$17.70
Purchase #2	$55.33	7.567%	$59.5168	$59.52	$59.50	$59.50
Purchase #3	$100.38	12.746%	$113.1744	$113.17	$113.15	$113.20
Purchase #4	$39.30	11.538%	$43.8344	$43.83	$43.85	$43.80
Purchase #5	$30.67	9.636%	$33.6254	$33.63	$33.65	$33.60
Purchase #6	$104.37	8.407%	$113.1444	$113.14	$113.15	$113.10
Purchase #7	$56.46	12.554%	$63.548	$63.55	$63.55	$63.50
7 purchase totals =	$403.45		$444.5130	$444.51	$444.50	$444.40