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	$47.53	4.803%	$49.8129	$49.81	$49.80	$49.80
Purchase #2	$214.47	3.734%	$222.4783	$222.48	$222.50	$222.50
Purchase #3	$86.54	3.739%	$89.7757	$89.78	$89.80	$89.80
Purchase #4	$151.93	9.570%	$166.4697	$166.47	$166.45	$166.50
Purchase #5	$151.37	10.796%	$167.7119	$167.71	$167.70	$167.70
Purchase #6	$176.55	13.195%	$199.8458	$199.85	$199.85	$199.80
Purchase #7	$77.43	5.297%	$81.5315	$81.53	$81.55	$81.50
7 purchase totals =	$905.82		$977.6258	$977.63	$977.65	$977.60