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	$40.46	3.384%	$41.8292	$41.83	$41.85	$41.80
Purchase #2	$30.26	7.732%	$32.5997	$32.60	$32.60	$32.60
Purchase #3	$241.78	12.838%	$272.8197	$272.82	$272.80	$272.80
Purchase #4	$56.85	12.356%	$63.8744	$63.87	$63.85	$63.90
Purchase #5	$133.72	7.356%	$143.5564	$143.56	$143.55	$143.60
Purchase #6	$217.81	3.263%	$224.9171	$224.92	$224.90	$224.90
Purchase #7	$170.98	10.797%	$189.4407	$189.44	$189.45	$189.40
7 purchase totals =	$891.86		$969.0372	$969.04	$969.00	$969.00