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	$59.30	10.476%	$65.5123	$65.51	$65.50	$65.50
Purchase #2	$137.35	10.616%	$151.9311	$151.93	$151.95	$151.90
Purchase #3	$228.75	11.701%	$255.516	$255.52	$255.50	$255.50
Purchase #4	$58.43	8.573%	$63.4392	$63.44	$63.45	$63.40
Purchase #5	$231.68	13.660%	$263.3275	$263.33	$263.35	$263.30
Purchase #6	$34.86	3.561%	$36.1014	$36.10	$36.10	$36.10
Purchase #7	$44.97	4.112%	$46.8192	$46.82	$46.80	$46.80
7 purchase totals =	$795.34		$882.6467	$882.65	$882.65	$882.50