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	$222.72	11.164%	$247.5845	$247.58	$247.60	$247.60
Purchase #2	$64.61	4.396%	$67.4503	$67.45	$67.45	$67.50
Purchase #3	$154.72	5.278%	$162.8861	$162.89	$162.90	$162.90
Purchase #4	$75.68	10.729%	$83.7997	$83.80	$83.80	$83.80
Purchase #5	$217.31	9.447%	$237.8393	$237.84	$237.85	$237.80
Purchase #6	$37.85	5.283%	$39.8496	$39.85	$39.85	$39.80
Purchase #7	$240.99	8.717%	$261.9971	$262.00	$262.00	$262.00
7 purchase totals =	$1,013.88		$1,101.4066	$1,101.41	$1,101.45	$1,101.40