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	$168.66	12.737%	$190.1422	$190.14	$190.15	$190.10
Purchase #2	$117.32	4.389%	$122.4692	$122.47	$122.45	$122.50
Purchase #3	$134.90	6.408%	$143.5444	$143.54	$143.55	$143.50
Purchase #4	$169.92	12.614%	$191.3537	$191.35	$191.35	$191.40
Purchase #5	$191.86	10.611%	$212.2183	$212.22	$212.20	$212.20
Purchase #6	$123.97	6.111%	$131.5458	$131.55	$131.55	$131.50
Purchase #7	$241.82	7.653%	$260.3265	$260.33	$260.35	$260.30
7 purchase totals =	$1,148.45		$1,251.6001	$1,251.60	$1,251.60	$1,251.50