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	$62.91	11.734%	$70.2919	$70.29	$70.30	$70.30
Purchase #2	$10.42	7.826%	$11.2355	$11.24	$11.25	$11.20
Purchase #3	$243.65	4.720%	$255.1503	$255.15	$255.15	$255.20
Purchase #4	$139.30	4.308%	$145.301	$145.30	$145.30	$145.30
Purchase #5	$35.59	11.234%	$39.5882	$39.59	$39.60	$39.60
Purchase #6	$220.65	12.682%	$248.6328	$248.63	$248.65	$248.60
Purchase #7	$94.29	11.745%	$105.3644	$105.36	$105.35	$105.40
7 purchase totals =	$806.81		$875.5641	$875.56	$875.60	$875.60