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	$217.52	6.587%	$231.848	$231.85	$231.85	$231.80
Purchase #2	$47.45	8.632%	$51.5459	$51.55	$51.55	$51.50
Purchase #3	$37.53	11.403%	$41.8095	$41.81	$41.80	$41.80
Purchase #4	$73.46	6.690%	$78.3745	$78.37	$78.35	$78.40
Purchase #5	$33.92	11.119%	$37.6916	$37.69	$37.70	$37.70
Purchase #6	$175.57	11.787%	$196.2644	$196.26	$196.25	$196.30
Purchase #7	$67.53	4.447%	$70.5331	$70.53	$70.55	$70.50
7 purchase totals =	$652.98		$708.0670	$708.06	$708.05	$708.00