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	$154.25	8.797%	$167.8194	$167.82	$167.80	$167.80
Purchase #2	$100.93	3.108%	$104.0669	$104.07	$104.05	$104.10
Purchase #3	$137.57	13.606%	$156.2878	$156.29	$156.30	$156.30
Purchase #4	$200.74	13.112%	$227.061	$227.06	$227.05	$227.10
Purchase #5	$60.25	3.517%	$62.369	$62.37	$62.35	$62.40
Purchase #6	$37.38	7.527%	$40.1936	$40.19	$40.20	$40.20
Purchase #7	$87.59	3.618%	$90.759	$90.76	$90.75	$90.80
7 purchase totals =	$778.71		$848.5567	$848.56	$848.50	$848.70