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	$219.86	4.756%	$230.3165	$230.32	$230.30	$230.30
Purchase #2	$50.61	4.392%	$52.8328	$52.83	$52.85	$52.80
Purchase #3	$152.67	10.411%	$168.5645	$168.56	$168.55	$168.60
Purchase #4	$97.55	7.387%	$104.756	$104.76	$104.75	$104.80
Purchase #5	$224.59	13.619%	$255.1769	$255.18	$255.20	$255.20
Purchase #6	$62.27	10.256%	$68.6564	$68.66	$68.65	$68.70
Purchase #7	$62.70	6.151%	$66.5567	$66.56	$66.55	$66.60
7 purchase totals =	$870.25		$946.8598	$946.87	$946.85	$947.00