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	$108.35	8.584%	$117.6508	$117.65	$117.65	$117.70
Purchase #2	$97.78	11.659%	$109.1802	$109.18	$109.20	$109.20
Purchase #3	$218.46	11.477%	$243.5327	$243.53	$243.55	$243.50
Purchase #4	$72.28	8.732%	$78.5915	$78.59	$78.60	$78.60
Purchase #5	$118.29	11.328%	$131.6899	$131.69	$131.70	$131.70
Purchase #6	$248.68	3.421%	$257.1873	$257.19	$257.20	$257.20
Purchase #7	$29.63	6.497%	$31.5551	$31.56	$31.55	$31.60
7 purchase totals =	$893.47		$969.3875	$969.39	$969.45	$969.50