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	$144.42	13.847%	$164.4178	$164.42	$164.40	$164.40
Purchase #2	$158.70	5.450%	$167.3492	$167.35	$167.35	$167.30
Purchase #3	$5.45	9.434%	$5.9642	$5.96	$5.95	$6.00
Purchase #4	$133.37	5.629%	$140.8774	$140.88	$140.90	$140.90
Purchase #5	$91.87	13.189%	$103.9867	$103.99	$104.00	$104.00
Purchase #6	$144.92	13.535%	$164.5349	$164.53	$164.55	$164.50
Purchase #7	$219.66	5.357%	$231.4272	$231.43	$231.45	$231.40
7 purchase totals =	$898.39		$978.5574	$978.56	$978.60	$978.50