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	$29.92	5.720%	$31.6314	$31.63	$31.65	$31.60
Purchase #2	$247.94	4.169%	$258.2766	$258.28	$258.30	$258.30
Purchase #3	$231.60	6.604%	$246.8949	$246.89	$246.90	$246.90
Purchase #4	$114.27	11.613%	$127.5402	$127.54	$127.55	$127.50
Purchase #5	$52.51	13.244%	$59.4644	$59.46	$59.45	$59.50
Purchase #6	$187.72	7.665%	$202.1087	$202.11	$202.10	$202.10
Purchase #7	$244.75	6.139%	$259.7752	$259.78	$259.80	$259.80
7 purchase totals =	$1,108.71		$1,185.6914	$1,185.69	$1,185.75	$1,185.70