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	$246.57	3.705%	$255.7054	$255.71	$255.70	$255.70
Purchase #2	$177.94	10.217%	$196.1201	$196.12	$196.10	$196.10
Purchase #3	$41.97	7.447%	$45.0955	$45.10	$45.10	$45.10
Purchase #4	$208.79	10.721%	$231.1744	$231.17	$231.15	$231.20
Purchase #5	$25.49	13.590%	$28.9541	$28.95	$28.95	$29.00
Purchase #6	$156.67	12.204%	$175.79	$175.79	$175.80	$175.80
Purchase #7	$95.50	7.407%	$102.5737	$102.57	$102.55	$102.60
7 purchase totals =	$952.93		$1,035.4132	$1,035.41	$1,035.35	$1,035.50