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	$14.33	10.672%	$15.8593	$15.86	$15.85	$15.90
Purchase #2	$72.87	8.121%	$78.7878	$78.79	$78.80	$78.80
Purchase #3	$96.82	10.858%	$107.3327	$107.33	$107.35	$107.30
Purchase #4	$126.67	12.716%	$142.7774	$142.78	$142.80	$142.80
Purchase #5	$184.76	3.250%	$190.7647	$190.76	$190.75	$190.80
Purchase #6	$162.70	13.504%	$184.671	$184.67	$184.65	$184.70
Purchase #7	$147.83	5.738%	$156.3125	$156.31	$156.30	$156.30
7 purchase totals =	$805.98		$876.5054	$876.50	$876.50	$876.60