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	$134.59	11.412%	$149.9494	$149.95	$149.95	$149.90
Purchase #2	$78.40	5.443%	$82.6673	$82.67	$82.65	$82.70
Purchase #3	$123.67	11.826%	$138.2952	$138.30	$138.30	$138.30
Purchase #4	$124.71	5.630%	$131.7312	$131.73	$131.75	$131.70
Purchase #5	$244.29	4.664%	$255.6837	$255.68	$255.70	$255.70
Purchase #6	$72.37	12.652%	$81.5263	$81.53	$81.55	$81.50
Purchase #7	$50.50	9.395%	$55.2445	$55.24	$55.25	$55.20
7 purchase totals =	$828.53		$895.0976	$895.10	$895.15	$895.00