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	$142.92	10.217%	$157.5221	$157.52	$157.50	$157.50
Purchase #2	$116.69	13.502%	$132.4455	$132.45	$132.45	$132.40
Purchase #3	$226.48	3.320%	$233.9991	$234.00	$234.00	$234.00
Purchase #4	$181.32	7.157%	$194.2971	$194.30	$194.30	$194.30
Purchase #5	$14.45	3.205%	$14.9131	$14.91	$14.90	$14.90
Purchase #6	$81.81	4.636%	$85.6027	$85.60	$85.60	$85.60
Purchase #7	$205.85	7.711%	$221.7231	$221.72	$221.70	$221.70
7 purchase totals =	$969.52		$1,040.5027	$1,040.50	$1,040.45	$1,040.40