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	$105.56	10.735%	$116.8919	$116.89	$116.90	$116.90
Purchase #2	$74.67	10.686%	$82.6492	$82.65	$82.65	$82.60
Purchase #3	$177.53	3.818%	$184.3081	$184.31	$184.30	$184.30
Purchase #4	$176.59	6.255%	$187.6357	$187.64	$187.65	$187.60
Purchase #5	$136.75	13.866%	$155.7118	$155.71	$155.70	$155.70
Purchase #6	$176.52	13.539%	$200.419	$200.42	$200.40	$200.40
Purchase #7	$47.26	8.729%	$51.3853	$51.39	$51.40	$51.40
7 purchase totals =	$894.88		$979.0010	$979.01	$979.00	$978.90