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	$244.76	6.810%	$261.4282	$261.43	$261.45	$261.40
Purchase #2	$29.58	6.366%	$31.4631	$31.46	$31.45	$31.50
Purchase #3	$42.51	6.548%	$45.2936	$45.29	$45.30	$45.30
Purchase #4	$203.70	3.313%	$210.4486	$210.45	$210.45	$210.40
Purchase #5	$43.27	4.595%	$45.2583	$45.26	$45.25	$45.30
Purchase #6	$122.43	8.253%	$132.5341	$132.53	$132.55	$132.50
Purchase #7	$125.52	12.631%	$141.3744	$141.37	$141.35	$141.40
7 purchase totals =	$811.77		$867.8003	$867.79	$867.80	$867.80