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	$138.68	9.868%	$152.3649	$152.36	$152.35	$152.40
Purchase #2	$223.37	9.570%	$244.7465	$244.75	$244.75	$244.70
Purchase #3	$159.92	10.616%	$176.8971	$176.90	$176.90	$176.90
Purchase #4	$13.79	9.143%	$15.0508	$15.05	$15.05	$15.10
Purchase #5	$95.28	7.534%	$102.4584	$102.46	$102.45	$102.50
Purchase #6	$115.50	3.378%	$119.4016	$119.40	$119.40	$119.40
Purchase #7	$208.59	6.665%	$222.4925	$222.49	$222.50	$222.50
7 purchase totals =	$955.13		$1,033.4118	$1,033.41	$1,033.40	$1,033.50