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	$240.90	4.384%	$251.4611	$251.46	$251.45	$251.50
Purchase #2	$62.67	6.590%	$66.8	$66.80	$66.80	$66.80
Purchase #3	$186.27	5.555%	$196.6173	$196.62	$196.60	$196.60
Purchase #4	$220.98	10.676%	$244.5718	$244.57	$244.55	$244.60
Purchase #5	$155.82	10.732%	$172.5426	$172.54	$172.55	$172.50
Purchase #6	$47.77	12.725%	$53.8487	$53.85	$53.85	$53.80
Purchase #7	$129.70	8.217%	$140.3574	$140.36	$140.35	$140.40
7 purchase totals =	$1,044.11		$1,126.1989	$1,126.20	$1,126.15	$1,126.20