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	$216.78	10.694%	$239.9625	$239.96	$239.95	$240.00
Purchase #2	$15.32	3.527%	$15.8603	$15.86	$15.85	$15.90
Purchase #3	$177.40	6.453%	$188.8476	$188.85	$188.85	$188.80
Purchase #4	$157.68	10.239%	$173.8249	$173.82	$173.80	$173.80
Purchase #5	$212.79	5.685%	$224.8871	$224.89	$224.90	$224.90
Purchase #6	$123.63	6.193%	$131.2864	$131.29	$131.30	$131.30
Purchase #7	$25.34	13.172%	$28.6778	$28.68	$28.70	$28.70
7 purchase totals =	$928.94		$1,003.3466	$1,003.35	$1,003.35	$1,003.40