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	$90.81	3.350%	$93.8521	$93.85	$93.85	$93.90
Purchase #2	$31.93	8.873%	$34.7631	$34.76	$34.75	$34.80
Purchase #3	$196.98	7.541%	$211.8343	$211.83	$211.85	$211.80
Purchase #4	$234.77	11.835%	$262.555	$262.56	$262.55	$262.60
Purchase #5	$229.60	4.322%	$239.5233	$239.52	$239.50	$239.50
Purchase #6	$143.38	11.323%	$159.6149	$159.61	$159.60	$159.60
Purchase #7	$59.67	5.385%	$62.8832	$62.88	$62.90	$62.90
7 purchase totals =	$987.14		$1,065.0259	$1,065.01	$1,065.00	$1,065.10