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	$142.74	8.168%	$154.399	$154.40	$154.40	$154.40
Purchase #2	$87.87	3.346%	$90.8101	$90.81	$90.80	$90.80
Purchase #3	$47.84	6.800%	$51.0931	$51.09	$51.10	$51.10
Purchase #4	$71.86	9.410%	$78.622	$78.62	$78.60	$78.60
Purchase #5	$138.40	12.727%	$156.0142	$156.01	$156.00	$156.00
Purchase #6	$201.61	4.422%	$210.5252	$210.53	$210.55	$210.50
Purchase #7	$10.49	11.587%	$11.7055	$11.71	$11.70	$11.70
7 purchase totals =	$700.81		$753.1691	$753.17	$753.15	$753.10