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	$152.63	10.667%	$168.911	$168.91	$168.90	$168.90
Purchase #2	$129.80	5.394%	$136.8014	$136.80	$136.80	$136.80
Purchase #3	$164.72	12.520%	$185.3429	$185.34	$185.35	$185.30
Purchase #4	$238.55	4.156%	$248.4641	$248.46	$248.45	$248.50
Purchase #5	$13.70	9.526%	$15.0051	$15.01	$15.00	$15.00
Purchase #6	$90.54	7.418%	$97.2563	$97.26	$97.25	$97.30
Purchase #7	$123.59	6.395%	$131.4936	$131.49	$131.50	$131.50
7 purchase totals =	$913.53		$983.2744	$983.27	$983.25	$983.30