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	$187.91	9.349%	$205.4777	$205.48	$205.50	$205.50
Purchase #2	$131.65	4.497%	$137.5703	$137.57	$137.55	$137.60
Purchase #3	$126.69	4.590%	$132.5051	$132.51	$132.50	$132.50
Purchase #4	$40.32	5.289%	$42.4525	$42.45	$42.45	$42.50
Purchase #5	$215.79	7.287%	$231.5146	$231.51	$231.50	$231.50
Purchase #6	$7.42	7.763%	$7.996	$8.00	$8.00	$8.00
Purchase #7	$228.67	8.555%	$248.2327	$248.23	$248.25	$248.20
7 purchase totals =	$938.45		$1,005.7489	$1,005.75	$1,005.75	$1,005.80