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	$92.90	3.440%	$96.0958	$96.10	$96.10	$96.10
Purchase #2	$145.51	10.281%	$160.4699	$160.47	$160.45	$160.50
Purchase #3	$207.75	8.279%	$224.9496	$224.95	$224.95	$224.90
Purchase #4	$116.32	6.422%	$123.7901	$123.79	$123.80	$123.80
Purchase #5	$162.54	9.825%	$178.5096	$178.51	$178.50	$178.50
Purchase #6	$123.99	5.661%	$131.0091	$131.01	$131.00	$131.00
Purchase #7	$140.89	10.602%	$155.8272	$155.83	$155.85	$155.80
7 purchase totals =	$989.90		$1,070.6513	$1,070.66	$1,070.65	$1,070.60