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	$97.27	13.405%	$110.309	$110.31	$110.30	$110.30
Purchase #2	$153.52	3.564%	$158.9915	$158.99	$159.00	$159.00
Purchase #3	$131.32	10.273%	$144.8105	$144.81	$144.80	$144.80
Purchase #4	$109.65	6.715%	$117.013	$117.01	$117.00	$117.00
Purchase #5	$98.29	13.527%	$111.5857	$111.59	$111.60	$111.60
Purchase #6	$243.76	11.352%	$271.4316	$271.43	$271.45	$271.40
Purchase #7	$201.42	7.204%	$215.9303	$215.93	$215.95	$215.90
7 purchase totals =	$1,035.23		$1,130.0716	$1,130.07	$1,130.10	$1,130.00