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	$58.56	4.179%	$61.0072	$61.01	$61.00	$61.00
Purchase #2	$35.31	13.307%	$40.0087	$40.01	$40.00	$40.00
Purchase #3	$36.47	13.807%	$41.5054	$41.51	$41.50	$41.50
Purchase #4	$10.87	5.212%	$11.4365	$11.44	$11.45	$11.40
Purchase #5	$104.49	13.522%	$118.6191	$118.62	$118.60	$118.60
Purchase #6	$44.50	5.451%	$46.9257	$46.93	$46.95	$46.90
Purchase #7	$238.59	5.357%	$251.3713	$251.37	$251.35	$251.40
7 purchase totals =	$528.79		$570.8739	$570.89	$570.85	$570.80