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	$149.39	10.349%	$164.8504	$164.85	$164.85	$164.90
Purchase #2	$112.73	13.554%	$128.0094	$128.01	$128.00	$128.00
Purchase #3	$64.85	3.397%	$67.053	$67.05	$67.05	$67.10
Purchase #4	$153.51	12.632%	$172.9014	$172.90	$172.90	$172.90
Purchase #5	$87.85	12.601%	$98.92	$98.92	$98.90	$98.90
Purchase #6	$122.63	12.262%	$137.6669	$137.67	$137.65	$137.70
Purchase #7	$239.39	9.831%	$262.9244	$262.92	$262.90	$262.90
7 purchase totals =	$930.35		$1,032.3255	$1,032.32	$1,032.25	$1,032.40