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	$38.77	11.150%	$43.0929	$43.09	$43.10	$43.10
Purchase #2	$114.69	10.767%	$127.0387	$127.04	$127.05	$127.00
Purchase #3	$235.78	4.103%	$245.4541	$245.45	$245.45	$245.50
Purchase #4	$99.58	4.683%	$104.2433	$104.24	$104.25	$104.20
Purchase #5	$98.92	8.190%	$107.0215	$107.02	$107.00	$107.00
Purchase #6	$176.43	12.807%	$199.0254	$199.03	$199.05	$199.00
Purchase #7	$142.39	5.396%	$150.0734	$150.07	$150.05	$150.10
7 purchase totals =	$906.56		$975.9493	$975.94	$975.95	$975.90