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	$99.32	5.142%	$104.427	$104.43	$104.45	$104.40
Purchase #2	$43.57	11.826%	$48.7226	$48.72	$48.70	$48.70
Purchase #3	$111.99	10.764%	$124.0446	$124.04	$124.05	$124.00
Purchase #4	$128.78	12.558%	$144.9522	$144.95	$144.95	$145.00
Purchase #5	$137.25	4.720%	$143.7282	$143.73	$143.75	$143.70
Purchase #6	$97.67	12.548%	$109.9256	$109.93	$109.95	$109.90
Purchase #7	$210.25	12.168%	$235.8332	$235.83	$235.85	$235.80
7 purchase totals =	$828.83		$911.6334	$911.63	$911.70	$911.50