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	$174.32	8.105%	$188.4486	$188.45	$188.45	$188.40
Purchase #2	$29.86	5.285%	$31.4381	$31.44	$31.45	$31.40
Purchase #3	$115.79	6.313%	$123.0998	$123.10	$123.10	$123.10
Purchase #4	$150.33	3.694%	$155.8832	$155.88	$155.90	$155.90
Purchase #5	$132.49	4.522%	$138.4812	$138.48	$138.50	$138.50
Purchase #6	$191.50	13.559%	$217.4655	$217.47	$217.45	$217.50
Purchase #7	$79.48	10.474%	$87.8047	$87.80	$87.80	$87.80
7 purchase totals =	$873.77		$942.6211	$942.62	$942.65	$942.60