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	$209.37	4.848%	$219.5203	$219.52	$219.50	$219.50
Purchase #2	$88.54	13.446%	$100.4451	$100.45	$100.45	$100.40
Purchase #3	$154.93	3.559%	$160.444	$160.44	$160.45	$160.40
Purchase #4	$39.42	10.792%	$43.6742	$43.67	$43.65	$43.70
Purchase #5	$77.67	6.559%	$82.7644	$82.76	$82.75	$82.80
Purchase #6	$213.58	6.289%	$227.012	$227.01	$227.00	$227.00
Purchase #7	$125.41	13.376%	$142.1848	$142.18	$142.20	$142.20
7 purchase totals =	$908.92		$976.0448	$976.03	$976.00	$976.00