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	$155.78	7.179%	$166.9634	$166.96	$166.95	$167.00
Purchase #2	$153.82	4.643%	$160.9619	$160.96	$160.95	$161.00
Purchase #3	$177.29	12.587%	$199.6055	$199.61	$199.60	$199.60
Purchase #4	$179.80	9.231%	$196.3973	$196.40	$196.40	$196.40
Purchase #5	$116.35	12.246%	$130.5982	$130.60	$130.60	$130.60
Purchase #6	$153.58	9.369%	$167.9689	$167.97	$167.95	$168.00
Purchase #7	$151.75	10.350%	$167.4561	$167.46	$167.45	$167.50
7 purchase totals =	$1,088.37		$1,189.9513	$1,189.96	$1,189.90	$1,190.10