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	$55.83	10.608%	$61.7524	$61.75	$61.75	$61.80
Purchase #2	$208.69	13.730%	$237.3431	$237.34	$237.35	$237.30
Purchase #3	$137.52	3.840%	$142.8008	$142.80	$142.80	$142.80
Purchase #4	$216.40	3.432%	$223.8268	$223.83	$223.85	$223.80
Purchase #5	$134.74	6.725%	$143.8013	$143.80	$143.80	$143.80
Purchase #6	$48.95	5.516%	$51.6501	$51.65	$51.65	$51.70
Purchase #7	$61.54	9.422%	$67.3383	$67.34	$67.35	$67.30
7 purchase totals =	$863.67		$928.5128	$928.51	$928.55	$928.50