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	$117.43	6.383%	$124.9256	$124.93	$124.95	$124.90
Purchase #2	$119.32	9.338%	$130.4621	$130.46	$130.45	$130.50
Purchase #3	$23.85	6.596%	$25.4231	$25.42	$25.40	$25.40
Purchase #4	$234.39	9.166%	$255.8742	$255.87	$255.85	$255.90
Purchase #5	$222.89	5.387%	$234.8971	$234.90	$234.90	$234.90
Purchase #6	$127.72	8.167%	$138.1509	$138.15	$138.15	$138.20
Purchase #7	$57.57	13.819%	$65.5256	$65.53	$65.55	$65.50
7 purchase totals =	$903.17		$975.2586	$975.26	$975.25	$975.30