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	$239.44	6.597%	$255.2359	$255.24	$255.25	$255.20
Purchase #2	$123.44	3.520%	$127.7851	$127.79	$127.80	$127.80
Purchase #3	$199.56	7.268%	$214.064	$214.06	$214.05	$214.10
Purchase #4	$197.98	12.542%	$222.8107	$222.81	$222.80	$222.80
Purchase #5	$9.67	8.228%	$10.4656	$10.47	$10.45	$10.50
Purchase #6	$59.97	13.843%	$68.2716	$68.27	$68.25	$68.30
Purchase #7	$117.67	11.872%	$131.6398	$131.64	$131.65	$131.60
7 purchase totals =	$947.73		$1,030.2727	$1,030.28	$1,030.25	$1,030.30