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	$31.81	9.610%	$34.8669	$34.87	$34.85	$34.90
Purchase #2	$52.79	6.844%	$56.4029	$56.40	$56.40	$56.40
Purchase #3	$40.89	13.536%	$46.4249	$46.42	$46.40	$46.40
Purchase #4	$220.34	3.222%	$227.4394	$227.44	$227.45	$227.40
Purchase #5	$162.40	5.443%	$171.2394	$171.24	$171.25	$171.20
Purchase #6	$83.84	13.489%	$95.1492	$95.15	$95.15	$95.10
Purchase #7	$105.96	6.552%	$112.9025	$112.90	$112.90	$112.90
7 purchase totals =	$698.03		$744.4252	$744.42	$744.40	$744.30