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	$15.36	4.249%	$16.0126	$16.01	$16.00	$16.00
Purchase #2	$186.90	11.587%	$208.5561	$208.56	$208.55	$208.60
Purchase #3	$167.57	5.319%	$176.483	$176.48	$176.50	$176.50
Purchase #4	$19.63	10.508%	$21.6927	$21.69	$21.70	$21.70
Purchase #5	$190.59	3.328%	$196.9328	$196.93	$196.95	$196.90
Purchase #6	$151.77	11.287%	$168.9003	$168.90	$168.90	$168.90
Purchase #7	$174.31	4.563%	$182.2638	$182.26	$182.25	$182.30
7 purchase totals =	$906.13		$970.8413	$970.83	$970.85	$970.90