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	$202.93	6.826%	$216.782	$216.78	$216.80	$216.80
Purchase #2	$241.60	9.638%	$264.8854	$264.89	$264.90	$264.90
Purchase #3	$186.98	7.395%	$200.8072	$200.81	$200.80	$200.80
Purchase #4	$239.32	9.602%	$262.2995	$262.30	$262.30	$262.30
Purchase #5	$127.69	12.810%	$144.0471	$144.05	$144.05	$144.00
Purchase #6	$190.89	4.757%	$199.9706	$199.97	$199.95	$200.00
Purchase #7	$164.77	11.549%	$183.7993	$183.80	$183.80	$183.80
7 purchase totals =	$1,354.18		$1,472.5911	$1,472.60	$1,472.60	$1,472.60