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	$138.50	8.634%	$150.4581	$150.46	$150.45	$150.50
Purchase #2	$125.48	5.469%	$132.3425	$132.34	$132.35	$132.30
Purchase #3	$192.99	6.334%	$205.214	$205.21	$205.20	$205.20
Purchase #4	$83.76	4.445%	$87.4831	$87.48	$87.50	$87.50
Purchase #5	$191.64	6.650%	$204.3841	$204.38	$204.40	$204.40
Purchase #6	$81.65	5.104%	$85.8174	$85.82	$85.80	$85.80
Purchase #7	$53.51	11.300%	$59.5566	$59.56	$59.55	$59.60
7 purchase totals =	$867.53		$925.2558	$925.25	$925.25	$925.30