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	$171.72	9.172%	$187.4702	$187.47	$187.45	$187.50
Purchase #2	$151.33	3.194%	$156.1635	$156.16	$156.15	$156.20
Purchase #3	$70.33	12.138%	$78.8667	$78.87	$78.85	$78.90
Purchase #4	$245.38	4.138%	$255.5338	$255.53	$255.55	$255.50
Purchase #5	$139.59	11.582%	$155.7573	$155.76	$155.75	$155.80
Purchase #6	$21.68	10.650%	$23.9889	$23.99	$24.00	$24.00
Purchase #7	$198.34	9.747%	$217.6722	$217.67	$217.65	$217.70
7 purchase totals =	$998.37		$1,075.4526	$1,075.45	$1,075.40	$1,075.60