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	$38.31	8.552%	$41.5863	$41.59	$41.60	$41.60
Purchase #2	$52.80	12.855%	$59.5874	$59.59	$59.60	$59.60
Purchase #3	$37.65	4.305%	$39.2708	$39.27	$39.25	$39.30
Purchase #4	$131.75	12.397%	$148.083	$148.08	$148.10	$148.10
Purchase #5	$9.45	7.669%	$10.1747	$10.17	$10.15	$10.20
Purchase #6	$191.29	13.147%	$216.4389	$216.44	$216.45	$216.40
Purchase #7	$152.83	5.358%	$161.0186	$161.02	$161.00	$161.00
7 purchase totals =	$614.08		$676.1597	$676.16	$676.15	$676.20