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	$82.90	7.544%	$89.154	$89.15	$89.15	$89.20
Purchase #2	$9.45	9.540%	$10.3515	$10.35	$10.35	$10.40
Purchase #3	$242.42	13.322%	$274.7152	$274.72	$274.70	$274.70
Purchase #4	$201.95	8.666%	$219.451	$219.45	$219.45	$219.50
Purchase #5	$77.30	4.757%	$80.9772	$80.98	$81.00	$81.00
Purchase #6	$101.80	10.387%	$112.374	$112.37	$112.35	$112.40
Purchase #7	$226.67	12.595%	$255.2191	$255.22	$255.20	$255.20
7 purchase totals =	$942.49		$1,042.2420	$1,042.24	$1,042.20	$1,042.40