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	$125.63	5.177%	$132.1339	$132.13	$132.15	$132.10
Purchase #2	$131.63	8.300%	$142.5553	$142.56	$142.55	$142.60
Purchase #3	$100.96	12.788%	$113.8708	$113.87	$113.85	$113.90
Purchase #4	$109.56	12.708%	$123.4829	$123.48	$123.50	$123.50
Purchase #5	$141.39	8.872%	$153.9341	$153.93	$153.95	$153.90
Purchase #6	$29.41	9.332%	$32.1545	$32.15	$32.15	$32.20
Purchase #7	$242.74	10.737%	$268.803	$268.80	$268.80	$268.80
7 purchase totals =	$881.32		$966.9345	$966.92	$966.95	$967.00