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	$217.48	10.831%	$241.0353	$241.04	$241.05	$241.00
Purchase #2	$59.56	12.288%	$66.8787	$66.88	$66.90	$66.90
Purchase #3	$131.39	4.705%	$137.5719	$137.57	$137.55	$137.60
Purchase #4	$107.88	3.677%	$111.8467	$111.85	$111.85	$111.80
Purchase #5	$87.88	10.789%	$97.3614	$97.36	$97.35	$97.40
Purchase #6	$135.46	6.209%	$143.8707	$143.87	$143.85	$143.90
Purchase #7	$222.70	10.678%	$246.4799	$246.48	$246.50	$246.50
7 purchase totals =	$962.35		$1,045.0446	$1,045.05	$1,045.05	$1,045.10