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	$117.83	11.402%	$131.265	$131.27	$131.25	$131.30
Purchase #2	$14.32	10.143%	$15.7725	$15.77	$15.75	$15.80
Purchase #3	$104.59	13.267%	$118.466	$118.47	$118.45	$118.50
Purchase #4	$41.43	4.592%	$43.3325	$43.33	$43.35	$43.30
Purchase #5	$57.28	11.327%	$63.7681	$63.77	$63.75	$63.80
Purchase #6	$232.52	12.696%	$262.0407	$262.04	$262.05	$262.00
Purchase #7	$103.79	5.778%	$109.787	$109.79	$109.80	$109.80
7 purchase totals =	$671.76		$744.4318	$744.44	$744.40	$744.50