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	$108.73	3.522%	$112.5595	$112.56	$112.55	$112.60
Purchase #2	$207.72	11.542%	$231.695	$231.70	$231.70	$231.70
Purchase #3	$227.83	12.131%	$255.4681	$255.47	$255.45	$255.50
Purchase #4	$159.96	7.626%	$172.1585	$172.16	$172.15	$172.20
Purchase #5	$105.39	8.250%	$114.0847	$114.08	$114.10	$114.10
Purchase #6	$45.77	12.454%	$51.4702	$51.47	$51.45	$51.50
Purchase #7	$111.38	4.407%	$116.2885	$116.29	$116.30	$116.30
7 purchase totals =	$966.78		$1,053.7245	$1,053.73	$1,053.70	$1,053.90