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	$61.56	6.205%	$65.3798	$65.38	$65.40	$65.40
Purchase #2	$10.50	7.839%	$11.3231	$11.32	$11.30	$11.30
Purchase #3	$235.47	13.185%	$266.5167	$266.52	$266.50	$266.50
Purchase #4	$224.85	11.582%	$250.8921	$250.89	$250.90	$250.90
Purchase #5	$163.96	7.654%	$176.5095	$176.51	$176.50	$176.50
Purchase #6	$200.29	4.344%	$208.9906	$208.99	$209.00	$209.00
Purchase #7	$16.79	8.522%	$18.2208	$18.22	$18.20	$18.20
7 purchase totals =	$913.42		$997.8326	$997.83	$997.80	$997.80