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	$86.31	10.626%	$95.4813	$95.48	$95.50	$95.50
Purchase #2	$42.47	10.158%	$46.7841	$46.78	$46.80	$46.80
Purchase #3	$15.54	10.200%	$17.1251	$17.13	$17.15	$17.10
Purchase #4	$43.54	4.209%	$45.3726	$45.37	$45.35	$45.40
Purchase #5	$87.75	3.808%	$91.0915	$91.09	$91.10	$91.10
Purchase #6	$204.80	10.262%	$225.8166	$225.82	$225.80	$225.80
Purchase #7	$189.57	10.768%	$209.9829	$209.98	$210.00	$210.00
7 purchase totals =	$669.98		$731.6541	$731.65	$731.70	$731.70