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	$13.43	3.476%	$13.8968	$13.90	$13.90	$13.90
Purchase #2	$123.37	10.745%	$136.6261	$136.63	$136.65	$136.60
Purchase #3	$59.28	5.399%	$62.4805	$62.48	$62.50	$62.50
Purchase #4	$68.55	12.795%	$77.321	$77.32	$77.30	$77.30
Purchase #5	$104.52	4.849%	$109.5882	$109.59	$109.60	$109.60
Purchase #6	$200.36	10.814%	$222.0269	$222.03	$222.05	$222.00
Purchase #7	$92.35	4.687%	$96.6784	$96.68	$96.70	$96.70
7 purchase totals =	$661.86		$718.6179	$718.63	$718.70	$718.60