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	$153.41	6.157%	$162.8555	$162.86	$162.85	$162.90
Purchase #2	$48.43	5.410%	$51.0501	$51.05	$51.05	$51.10
Purchase #3	$144.95	11.769%	$162.0092	$162.01	$162.00	$162.00
Purchase #4	$90.60	8.730%	$98.5094	$98.51	$98.50	$98.50
Purchase #5	$112.60	10.418%	$124.3307	$124.33	$124.35	$124.30
Purchase #6	$85.59	10.144%	$94.2722	$94.27	$94.25	$94.30
Purchase #7	$166.40	5.850%	$176.1344	$176.13	$176.15	$176.10
7 purchase totals =	$801.98		$869.1615	$869.16	$869.15	$869.20