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	$119.81	3.401%	$123.8847	$123.88	$123.90	$123.90
Purchase #2	$101.54	13.128%	$114.8702	$114.87	$114.85	$114.90
Purchase #3	$134.42	7.533%	$144.5459	$144.55	$144.55	$144.50
Purchase #4	$141.61	4.509%	$147.9952	$148.00	$148.00	$148.00
Purchase #5	$186.80	7.168%	$200.1898	$200.19	$200.20	$200.20
Purchase #6	$153.82	13.621%	$174.7718	$174.77	$174.75	$174.80
Purchase #7	$43.42	5.357%	$45.746	$45.75	$45.75	$45.70
7 purchase totals =	$881.42		$952.0036	$952.01	$952.00	$952.00