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	$81.37	9.473%	$89.0782	$89.08	$89.10	$89.10
Purchase #2	$194.67	11.780%	$217.6021	$217.60	$217.60	$217.60
Purchase #3	$174.85	7.271%	$187.5633	$187.56	$187.55	$187.60
Purchase #4	$152.91	3.686%	$158.5463	$158.55	$158.55	$158.50
Purchase #5	$72.70	12.488%	$81.7788	$81.78	$81.80	$81.80
Purchase #6	$58.70	12.702%	$66.1561	$66.16	$66.15	$66.20
Purchase #7	$246.80	4.840%	$258.7451	$258.75	$258.75	$258.70
7 purchase totals =	$982.00		$1,059.4699	$1,059.48	$1,059.50	$1,059.50