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	$82.32	11.564%	$91.8395	$91.84	$91.85	$91.80
Purchase #2	$186.65	11.725%	$208.5347	$208.53	$208.55	$208.50
Purchase #3	$74.37	3.715%	$77.1328	$77.13	$77.15	$77.10
Purchase #4	$92.83	8.577%	$100.792	$100.79	$100.80	$100.80
Purchase #5	$213.87	10.702%	$236.7584	$236.76	$236.75	$236.80
Purchase #6	$93.71	11.852%	$104.8165	$104.82	$104.80	$104.80
Purchase #7	$46.50	12.838%	$52.4697	$52.47	$52.45	$52.50
7 purchase totals =	$790.25		$872.3436	$872.34	$872.35	$872.30