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	$239.85	9.606%	$262.89	$262.89	$262.90	$262.90
Purchase #2	$218.27	13.736%	$248.2516	$248.25	$248.25	$248.30
Purchase #3	$34.84	4.458%	$36.3932	$36.39	$36.40	$36.40
Purchase #4	$134.48	3.377%	$139.0214	$139.02	$139.00	$139.00
Purchase #5	$99.84	7.115%	$106.9436	$106.94	$106.95	$106.90
Purchase #6	$86.85	4.163%	$90.4656	$90.47	$90.45	$90.50
Purchase #7	$186.91	7.184%	$200.3376	$200.34	$200.35	$200.30
7 purchase totals =	$1,001.04		$1,084.3030	$1,084.30	$1,084.30	$1,084.30