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	$52.64	5.585%	$55.5799	$55.58	$55.60	$55.60
Purchase #2	$143.78	12.768%	$162.1378	$162.14	$162.15	$162.10
Purchase #3	$196.83	13.626%	$223.6501	$223.65	$223.65	$223.70
Purchase #4	$118.98	7.806%	$128.2676	$128.27	$128.25	$128.30
Purchase #5	$200.63	5.587%	$211.8392	$211.84	$211.85	$211.80
Purchase #6	$155.86	6.189%	$165.5062	$165.51	$165.50	$165.50
Purchase #7	$188.81	10.639%	$208.8975	$208.90	$208.90	$208.90
7 purchase totals =	$1,057.53		$1,155.8783	$1,155.89	$1,155.90	$1,155.90