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	$230.84	13.709%	$262.4859	$262.49	$262.50	$262.50
Purchase #2	$67.35	9.725%	$73.8998	$73.90	$73.90	$73.90
Purchase #3	$149.25	13.137%	$168.857	$168.86	$168.85	$168.90
Purchase #4	$163.73	9.849%	$179.8558	$179.86	$179.85	$179.90
Purchase #5	$50.98	5.785%	$53.9292	$53.93	$53.95	$53.90
Purchase #6	$112.55	9.204%	$122.9091	$122.91	$122.90	$122.90
Purchase #7	$137.37	5.178%	$144.483	$144.48	$144.50	$144.50
7 purchase totals =	$912.07		$1,006.4198	$1,006.43	$1,006.45	$1,006.50