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	$208.93	4.548%	$218.4321	$218.43	$218.45	$218.40
Purchase #2	$221.32	4.716%	$231.7575	$231.76	$231.75	$231.80
Purchase #3	$103.78	10.863%	$115.0536	$115.05	$115.05	$115.10
Purchase #4	$162.67	3.404%	$168.2073	$168.21	$168.20	$168.20
Purchase #5	$10.33	12.351%	$11.6059	$11.61	$11.60	$11.60
Purchase #6	$69.37	13.727%	$78.8924	$78.89	$78.90	$78.90
Purchase #7	$86.75	6.671%	$92.5371	$92.54	$92.55	$92.50
7 purchase totals =	$863.15		$916.4859	$916.49	$916.50	$916.50