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	$125.80	13.318%	$142.554	$142.55	$142.55	$142.60
Purchase #2	$123.68	6.177%	$131.3197	$131.32	$131.30	$131.30
Purchase #3	$30.98	5.800%	$32.7768	$32.78	$32.80	$32.80
Purchase #4	$49.86	7.405%	$53.5521	$53.55	$53.55	$53.60
Purchase #5	$105.82	10.467%	$116.8962	$116.90	$116.90	$116.90
Purchase #6	$199.92	6.531%	$212.9768	$212.98	$213.00	$213.00
Purchase #7	$29.86	11.666%	$33.3435	$33.34	$33.35	$33.30
7 purchase totals =	$665.92		$723.4191	$723.42	$723.45	$723.50