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	$71.60	9.766%	$78.5925	$78.59	$78.60	$78.60
Purchase #2	$73.65	8.636%	$80.0104	$80.01	$80.00	$80.00
Purchase #3	$59.86	10.682%	$66.2542	$66.25	$66.25	$66.30
Purchase #4	$111.33	6.134%	$118.159	$118.16	$118.15	$118.20
Purchase #5	$32.95	10.414%	$36.3814	$36.38	$36.40	$36.40
Purchase #6	$107.58	4.563%	$112.4889	$112.49	$112.50	$112.50
Purchase #7	$206.65	12.799%	$233.0991	$233.10	$233.10	$233.10
7 purchase totals =	$663.62		$724.9855	$724.98	$725.00	$725.10