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	$154.85	9.369%	$169.3579	$169.36	$169.35	$169.40
Purchase #2	$134.30	6.821%	$143.4606	$143.46	$143.45	$143.50
Purchase #3	$127.48	13.450%	$144.6261	$144.63	$144.65	$144.60
Purchase #4	$199.53	6.864%	$213.2257	$213.23	$213.25	$213.20
Purchase #5	$95.83	10.252%	$105.6545	$105.65	$105.65	$105.70
Purchase #6	$86.43	3.778%	$89.6953	$89.70	$89.70	$89.70
Purchase #7	$110.43	3.141%	$113.8986	$113.90	$113.90	$113.90
7 purchase totals =	$908.85		$979.9187	$979.93	$979.95	$980.00