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	$179.75	4.823%	$188.4193	$188.42	$188.40	$188.40
Purchase #2	$81.94	10.372%	$90.4388	$90.44	$90.45	$90.40
Purchase #3	$56.28	3.824%	$58.4321	$58.43	$58.45	$58.40
Purchase #4	$105.25	8.208%	$113.8889	$113.89	$113.90	$113.90
Purchase #5	$14.42	3.821%	$14.971	$14.97	$14.95	$15.00
Purchase #6	$92.45	10.863%	$102.4928	$102.49	$102.50	$102.50
Purchase #7	$144.83	13.618%	$164.5529	$164.55	$164.55	$164.60
7 purchase totals =	$674.92		$733.1958	$733.19	$733.20	$733.20