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	$210.88	9.791%	$231.5273	$231.53	$231.55	$231.50
Purchase #2	$67.83	10.303%	$74.8185	$74.82	$74.80	$74.80
Purchase #3	$60.52	4.849%	$63.4546	$63.45	$63.45	$63.50
Purchase #4	$241.41	11.792%	$269.8771	$269.88	$269.90	$269.90
Purchase #5	$126.95	3.585%	$131.5012	$131.50	$131.50	$131.50
Purchase #6	$191.30	13.503%	$217.1312	$217.13	$217.15	$217.10
Purchase #7	$70.75	3.276%	$73.0678	$73.07	$73.05	$73.10
7 purchase totals =	$969.64		$1,061.3777	$1,061.38	$1,061.40	$1,061.40