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	$139.26	3.184%	$143.694	$143.69	$143.70	$143.70
Purchase #2	$66.56	7.543%	$71.5806	$71.58	$71.60	$71.60
Purchase #3	$213.78	12.851%	$241.2529	$241.25	$241.25	$241.30
Purchase #4	$231.79	11.870%	$259.3035	$259.30	$259.30	$259.30
Purchase #5	$87.27	12.840%	$98.4755	$98.48	$98.50	$98.50
Purchase #6	$99.43	12.657%	$112.0149	$112.01	$112.00	$112.00
Purchase #7	$105.58	7.581%	$113.584	$113.58	$113.60	$113.60
7 purchase totals =	$943.67		$1,039.9054	$1,039.89	$1,039.95	$1,040.00