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	$109.64	11.525%	$122.276	$122.28	$122.30	$122.30
Purchase #2	$145.68	6.817%	$155.611	$155.61	$155.60	$155.60
Purchase #3	$125.98	13.125%	$142.5149	$142.51	$142.50	$142.50
Purchase #4	$111.53	10.752%	$123.5217	$123.52	$123.50	$123.50
Purchase #5	$117.55	12.680%	$132.4553	$132.46	$132.45	$132.50
Purchase #6	$166.48	8.446%	$180.5409	$180.54	$180.55	$180.50
Purchase #7	$248.55	4.860%	$260.6295	$260.63	$260.65	$260.60
7 purchase totals =	$1,025.41		$1,117.5493	$1,117.55	$1,117.55	$1,117.50