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	$11.67	13.152%	$13.2048	$13.20	$13.20	$13.20
Purchase #2	$95.66	7.870%	$103.1884	$103.19	$103.20	$103.20
Purchase #3	$97.88	7.691%	$105.408	$105.41	$105.40	$105.40
Purchase #4	$51.85	11.277%	$57.6971	$57.70	$57.70	$57.70
Purchase #5	$65.59	5.127%	$68.9528	$68.95	$68.95	$69.00
Purchase #6	$67.98	4.584%	$71.0962	$71.10	$71.10	$71.10
Purchase #7	$20.63	13.768%	$23.4703	$23.47	$23.45	$23.50
7 purchase totals =	$411.26		$443.0176	$443.02	$443.00	$443.10