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	$142.57	9.760%	$156.4848	$156.48	$156.50	$156.50
Purchase #2	$80.37	12.390%	$90.3278	$90.33	$90.35	$90.30
Purchase #3	$11.80	6.390%	$12.554	$12.55	$12.55	$12.60
Purchase #4	$163.61	5.482%	$172.5791	$172.58	$172.60	$172.60
Purchase #5	$9.77	11.780%	$10.9209	$10.92	$10.90	$10.90
Purchase #6	$66.38	6.257%	$70.5334	$70.53	$70.55	$70.50
Purchase #7	$201.91	10.290%	$222.6865	$222.69	$222.70	$222.70
7 purchase totals =	$676.41		$736.0865	$736.08	$736.15	$736.10