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	$178.85	11.813%	$199.9776	$199.98	$200.00	$200.00
Purchase #2	$18.86	13.773%	$21.4576	$21.46	$21.45	$21.50
Purchase #3	$228.75	3.816%	$237.4791	$237.48	$237.50	$237.50
Purchase #4	$103.31	7.524%	$111.083	$111.08	$111.10	$111.10
Purchase #5	$148.91	10.119%	$163.9782	$163.98	$164.00	$164.00
Purchase #6	$221.70	10.737%	$245.5039	$245.50	$245.50	$245.50
Purchase #7	$42.84	9.451%	$46.8888	$46.89	$46.90	$46.90
7 purchase totals =	$943.22		$1,026.3682	$1,026.37	$1,026.45	$1,026.50