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	$39.57	9.341%	$43.2662	$43.27	$43.25	$43.30
Purchase #2	$216.99	3.192%	$223.9163	$223.92	$223.90	$223.90
Purchase #3	$210.78	3.650%	$218.4735	$218.47	$218.45	$218.50
Purchase #4	$217.66	6.304%	$231.3813	$231.38	$231.40	$231.40
Purchase #5	$163.84	8.563%	$177.8696	$177.87	$177.85	$177.90
Purchase #6	$153.26	12.163%	$171.901	$171.90	$171.90	$171.90
Purchase #7	$45.33	13.808%	$51.5892	$51.59	$51.60	$51.60
7 purchase totals =	$1,047.43		$1,118.3971	$1,118.40	$1,118.35	$1,118.50