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	$159.97	5.618%	$168.9571	$168.96	$168.95	$169.00
Purchase #2	$249.86	5.692%	$264.082	$264.08	$264.10	$264.10
Purchase #3	$24.72	12.427%	$27.792	$27.79	$27.80	$27.80
Purchase #4	$147.89	4.538%	$154.6012	$154.60	$154.60	$154.60
Purchase #5	$29.90	5.262%	$31.4733	$31.47	$31.45	$31.50
Purchase #6	$119.39	9.420%	$130.6365	$130.64	$130.65	$130.60
Purchase #7	$51.56	10.461%	$56.9537	$56.95	$56.95	$57.00
7 purchase totals =	$783.29		$834.4958	$834.49	$834.50	$834.60