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	$54.96	8.465%	$59.6124	$59.61	$59.60	$59.60
Purchase #2	$197.90	9.656%	$217.0092	$217.01	$217.00	$217.00
Purchase #3	$17.85	5.226%	$18.7828	$18.78	$18.80	$18.80
Purchase #4	$59.89	12.697%	$67.4942	$67.49	$67.50	$67.50
Purchase #5	$32.76	6.142%	$34.7721	$34.77	$34.75	$34.80
Purchase #6	$96.72	8.652%	$105.0882	$105.09	$105.10	$105.10
Purchase #7	$65.45	6.640%	$69.7959	$69.80	$69.80	$69.80
7 purchase totals =	$525.53		$572.5548	$572.55	$572.55	$572.60