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	$81.68	10.509%	$90.2638	$90.26	$90.25	$90.30
Purchase #2	$84.44	3.759%	$87.6141	$87.61	$87.60	$87.60
Purchase #3	$86.46	4.846%	$90.6499	$90.65	$90.65	$90.60
Purchase #4	$60.84	4.437%	$63.5395	$63.54	$63.55	$63.50
Purchase #5	$50.80	13.680%	$57.7494	$57.75	$57.75	$57.70
Purchase #6	$208.90	8.529%	$226.7171	$226.72	$226.70	$226.70
Purchase #7	$134.85	5.404%	$142.1373	$142.14	$142.15	$142.10
7 purchase totals =	$707.97		$758.6711	$758.67	$758.65	$758.50