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	$43.74	7.380%	$46.968	$46.97	$46.95	$47.00
Purchase #2	$246.58	3.799%	$255.9476	$255.95	$255.95	$255.90
Purchase #3	$74.81	10.188%	$82.4316	$82.43	$82.45	$82.40
Purchase #4	$34.82	10.733%	$38.5572	$38.56	$38.55	$38.60
Purchase #5	$104.88	6.606%	$111.8084	$111.81	$111.80	$111.80
Purchase #6	$31.49	4.618%	$32.9442	$32.94	$32.95	$32.90
Purchase #7	$101.90	13.600%	$115.7584	$115.76	$115.75	$115.80
7 purchase totals =	$638.22		$684.4154	$684.42	$684.40	$684.40