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	$231.90	12.446%	$260.7623	$260.76	$260.75	$260.80
Purchase #2	$96.87	8.313%	$104.9228	$104.92	$104.90	$104.90
Purchase #3	$6.75	10.141%	$7.4345	$7.43	$7.45	$7.40
Purchase #4	$103.72	13.697%	$117.9265	$117.93	$117.95	$117.90
Purchase #5	$232.68	12.845%	$262.5677	$262.57	$262.55	$262.60
Purchase #6	$162.89	13.167%	$184.3377	$184.34	$184.35	$184.30
Purchase #7	$117.33	8.720%	$127.5612	$127.56	$127.55	$127.60
7 purchase totals =	$952.14		$1,065.5127	$1,065.51	$1,065.50	$1,065.50