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	$98.31	9.254%	$107.4076	$107.41	$107.40	$107.40
Purchase #2	$179.50	3.190%	$185.2261	$185.23	$185.25	$185.20
Purchase #3	$175.81	11.739%	$196.4483	$196.45	$196.45	$196.40
Purchase #4	$129.55	10.542%	$143.2072	$143.21	$143.20	$143.20
Purchase #5	$121.66	3.759%	$126.2332	$126.23	$126.25	$126.20
Purchase #6	$217.40	9.259%	$237.5291	$237.53	$237.55	$237.50
Purchase #7	$83.72	7.808%	$90.2569	$90.26	$90.25	$90.30
7 purchase totals =	$1,005.95		$1,086.3084	$1,086.32	$1,086.35	$1,086.20