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	$122.65	3.620%	$127.0899	$127.09	$127.10	$127.10
Purchase #2	$86.76	9.374%	$94.8929	$94.89	$94.90	$94.90
Purchase #3	$117.54	11.761%	$131.3639	$131.36	$131.35	$131.40
Purchase #4	$177.83	5.168%	$187.0203	$187.02	$187.00	$187.00
Purchase #5	$222.68	7.397%	$239.1516	$239.15	$239.15	$239.20
Purchase #6	$132.68	3.477%	$137.2933	$137.29	$137.30	$137.30
Purchase #7	$70.75	11.175%	$78.6563	$78.66	$78.65	$78.70
7 purchase totals =	$930.89		$995.4682	$995.46	$995.45	$995.60