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	$14.72	6.576%	$15.688	$15.69	$15.70	$15.70
Purchase #2	$127.58	5.166%	$134.1708	$134.17	$134.15	$134.20
Purchase #3	$54.51	9.115%	$59.4786	$59.48	$59.50	$59.50
Purchase #4	$46.76	5.750%	$49.4487	$49.45	$49.45	$49.40
Purchase #5	$212.45	4.262%	$221.5046	$221.50	$221.50	$221.50
Purchase #6	$94.72	11.685%	$105.788	$105.79	$105.80	$105.80
Purchase #7	$131.25	10.331%	$144.8094	$144.81	$144.80	$144.80
7 purchase totals =	$681.99		$730.8881	$730.89	$730.90	$730.90