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	$68.66	5.394%	$72.3635	$72.36	$72.35	$72.40
Purchase #2	$180.71	6.497%	$192.4507	$192.45	$192.45	$192.50
Purchase #3	$143.56	12.706%	$161.8007	$161.80	$161.80	$161.80
Purchase #4	$56.43	10.694%	$62.4646	$62.46	$62.45	$62.50
Purchase #5	$11.89	8.241%	$12.8699	$12.87	$12.85	$12.90
Purchase #6	$100.44	10.516%	$111.0023	$111.00	$111.00	$111.00
Purchase #7	$147.80	9.232%	$161.4449	$161.44	$161.45	$161.40
7 purchase totals =	$709.49		$774.3966	$774.38	$774.35	$774.50