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	$55.49	12.425%	$62.3846	$62.38	$62.40	$62.40
Purchase #2	$57.39	13.510%	$65.1434	$65.14	$65.15	$65.10
Purchase #3	$61.84	9.692%	$67.8335	$67.83	$67.85	$67.80
Purchase #4	$97.84	6.638%	$104.3346	$104.33	$104.35	$104.30
Purchase #5	$66.76	8.795%	$72.6315	$72.63	$72.65	$72.60
Purchase #6	$25.67	5.709%	$27.1355	$27.14	$27.15	$27.10
Purchase #7	$38.95	4.407%	$40.6665	$40.67	$40.65	$40.70
7 purchase totals =	$403.94		$440.1296	$440.12	$440.20	$440.00