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	$94.39	6.831%	$100.8378	$100.84	$100.85	$100.80
Purchase #2	$221.55	5.462%	$233.6511	$233.65	$233.65	$233.70
Purchase #3	$75.64	9.659%	$82.9461	$82.95	$82.95	$82.90
Purchase #4	$135.31	12.434%	$152.1344	$152.13	$152.15	$152.10
Purchase #5	$117.50	9.756%	$128.9633	$128.96	$128.95	$129.00
Purchase #6	$166.89	10.210%	$183.9295	$183.93	$183.95	$183.90
Purchase #7	$236.84	13.845%	$269.6305	$269.63	$269.65	$269.60
7 purchase totals =	$1,048.12		$1,152.0927	$1,152.09	$1,152.15	$1,152.00