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	$159.79	4.510%	$166.9965	$167.00	$167.00	$167.00
Purchase #2	$142.65	9.812%	$156.6468	$156.65	$156.65	$156.60
Purchase #3	$10.92	6.286%	$11.6064	$11.61	$11.60	$11.60
Purchase #4	$210.55	6.648%	$224.5474	$224.55	$224.55	$224.50
Purchase #5	$49.71	10.375%	$54.8674	$54.87	$54.85	$54.90
Purchase #6	$75.31	11.269%	$83.7967	$83.80	$83.80	$83.80
Purchase #7	$228.69	6.520%	$243.6006	$243.60	$243.60	$243.60
7 purchase totals =	$877.62		$942.0618	$942.08	$942.05	$942.00