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	$103.93	6.867%	$111.0669	$111.07	$111.05	$111.10
Purchase #2	$248.80	12.344%	$279.5119	$279.51	$279.50	$279.50
Purchase #3	$80.38	6.367%	$85.4978	$85.50	$85.50	$85.50
Purchase #4	$135.63	6.581%	$144.5558	$144.56	$144.55	$144.60
Purchase #5	$137.51	13.139%	$155.5774	$155.58	$155.60	$155.60
Purchase #6	$248.89	5.201%	$261.8348	$261.83	$261.85	$261.80
Purchase #7	$177.46	12.508%	$199.6567	$199.66	$199.65	$199.70
7 purchase totals =	$1,132.60		$1,237.7013	$1,237.71	$1,237.70	$1,237.80