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	$165.54	9.680%	$181.5643	$181.56	$181.55	$181.60
Purchase #2	$74.91	12.136%	$84.0011	$84.00	$84.00	$84.00
Purchase #3	$172.96	5.862%	$183.0989	$183.10	$183.10	$183.10
Purchase #4	$127.69	10.834%	$141.5239	$141.52	$141.50	$141.50
Purchase #5	$151.29	11.151%	$168.1603	$168.16	$168.15	$168.20
Purchase #6	$134.86	11.868%	$150.8652	$150.87	$150.85	$150.90
Purchase #7	$32.49	12.618%	$36.5896	$36.59	$36.60	$36.60
7 purchase totals =	$859.74		$945.8033	$945.80	$945.75	$945.90