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	$240.78	4.427%	$251.4393	$251.44	$251.45	$251.40
Purchase #2	$146.72	6.874%	$156.8055	$156.81	$156.80	$156.80
Purchase #3	$132.82	8.771%	$144.4696	$144.47	$144.45	$144.50
Purchase #4	$87.96	10.705%	$97.3761	$97.38	$97.40	$97.40
Purchase #5	$128.39	10.629%	$142.0366	$142.04	$142.05	$142.00
Purchase #6	$32.89	4.357%	$34.323	$34.32	$34.30	$34.30
Purchase #7	$194.45	9.602%	$213.1211	$213.12	$213.10	$213.10
7 purchase totals =	$964.01		$1,039.5712	$1,039.58	$1,039.55	$1,039.50