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	$231.78	12.853%	$261.5707	$261.57	$261.55	$261.60
Purchase #2	$90.81	3.604%	$94.0828	$94.08	$94.10	$94.10
Purchase #3	$183.64	9.203%	$200.5404	$200.54	$200.55	$200.50
Purchase #4	$85.55	6.707%	$91.2878	$91.29	$91.30	$91.30
Purchase #5	$92.90	11.725%	$103.7925	$103.79	$103.80	$103.80
Purchase #6	$187.89	6.526%	$200.1517	$200.15	$200.15	$200.20
Purchase #7	$161.79	13.403%	$183.4747	$183.47	$183.45	$183.50
7 purchase totals =	$1,034.36		$1,134.9006	$1,134.89	$1,134.90	$1,135.00