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	$22.35	4.322%	$23.316	$23.32	$23.30	$23.30
Purchase #2	$112.97	9.410%	$123.6005	$123.60	$123.60	$123.60
Purchase #3	$112.40	13.693%	$127.7909	$127.79	$127.80	$127.80
Purchase #4	$80.72	6.167%	$85.698	$85.70	$85.70	$85.70
Purchase #5	$120.65	6.237%	$128.1749	$128.17	$128.15	$128.20
Purchase #6	$188.97	13.532%	$214.5414	$214.54	$214.55	$214.50
Purchase #7	$247.57	6.199%	$262.9169	$262.92	$262.90	$262.90
7 purchase totals =	$885.63		$966.0386	$966.04	$966.00	$966.00