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	$52.30	13.550%	$59.3867	$59.39	$59.40	$59.40
Purchase #2	$137.45	12.754%	$154.9804	$154.98	$155.00	$155.00
Purchase #3	$226.92	13.461%	$257.4657	$257.47	$257.45	$257.50
Purchase #4	$18.84	6.272%	$20.0216	$20.02	$20.00	$20.00
Purchase #5	$34.82	7.233%	$37.3385	$37.34	$37.35	$37.30
Purchase #6	$190.89	5.860%	$202.0762	$202.08	$202.10	$202.10
Purchase #7	$151.32	8.586%	$164.3123	$164.31	$164.30	$164.30
7 purchase totals =	$812.54		$895.5814	$895.59	$895.60	$895.60