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	$105.78	8.203%	$114.4571	$114.46	$114.45	$114.50
Purchase #2	$7.42	12.458%	$8.3444	$8.34	$8.35	$8.30
Purchase #3	$36.93	12.367%	$41.4971	$41.50	$41.50	$41.50
Purchase #4	$247.29	10.413%	$273.0403	$273.04	$273.05	$273.00
Purchase #5	$120.96	8.691%	$131.4726	$131.47	$131.45	$131.50
Purchase #6	$38.40	13.247%	$43.4868	$43.49	$43.50	$43.50
Purchase #7	$176.82	7.771%	$190.5607	$190.56	$190.55	$190.60
7 purchase totals =	$733.60		$802.8590	$802.86	$802.85	$802.90