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	$21.67	9.866%	$23.808	$23.81	$23.80	$23.80
Purchase #2	$188.34	5.103%	$197.951	$197.95	$197.95	$198.00
Purchase #3	$84.81	11.859%	$94.8676	$94.87	$94.85	$94.90
Purchase #4	$128.37	8.613%	$139.4265	$139.43	$139.45	$139.40
Purchase #5	$118.73	7.448%	$127.573	$127.57	$127.55	$127.60
Purchase #6	$83.42	7.444%	$89.6298	$89.63	$89.65	$89.60
Purchase #7	$108.76	4.402%	$113.5476	$113.55	$113.55	$113.50
7 purchase totals =	$734.10		$786.8035	$786.81	$786.80	$786.80