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	$28.69	9.617%	$31.4491	$31.45	$31.45	$31.40
Purchase #2	$213.47	9.326%	$233.3782	$233.38	$233.40	$233.40
Purchase #3	$102.71	3.288%	$106.0871	$106.09	$106.10	$106.10
Purchase #4	$217.45	6.636%	$231.88	$231.88	$231.90	$231.90
Purchase #5	$140.34	10.396%	$154.9297	$154.93	$154.95	$154.90
Purchase #6	$96.47	3.822%	$100.1571	$100.16	$100.15	$100.20
Purchase #7	$141.43	10.349%	$156.0666	$156.07	$156.05	$156.10
7 purchase totals =	$940.56		$1,013.9478	$1,013.96	$1,014.00	$1,014.00