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	$114.98	7.136%	$123.185	$123.19	$123.20	$123.20
Purchase #2	$17.80	6.491%	$18.9554	$18.96	$18.95	$19.00
Purchase #3	$12.37	12.676%	$13.938	$13.94	$13.95	$13.90
Purchase #4	$226.65	12.669%	$255.3643	$255.36	$255.35	$255.40
Purchase #5	$242.48	12.306%	$272.3196	$272.32	$272.30	$272.30
Purchase #6	$126.57	8.376%	$137.1715	$137.17	$137.15	$137.20
Purchase #7	$217.43	10.655%	$240.5972	$240.60	$240.60	$240.60
7 purchase totals =	$958.28		$1,061.5310	$1,061.54	$1,061.50	$1,061.60