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	$129.84	8.622%	$141.0348	$141.03	$141.05	$141.00
Purchase #2	$43.42	4.551%	$45.396	$45.40	$45.40	$45.40
Purchase #3	$131.53	4.423%	$137.3476	$137.35	$137.35	$137.30
Purchase #4	$30.30	10.705%	$33.5436	$33.54	$33.55	$33.50
Purchase #5	$189.33	11.196%	$210.5274	$210.53	$210.55	$210.50
Purchase #6	$9.83	12.403%	$11.0492	$11.05	$11.05	$11.00
Purchase #7	$172.97	5.661%	$182.7618	$182.76	$182.75	$182.80
7 purchase totals =	$707.22		$761.6604	$761.66	$761.70	$761.50