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	$60.80	3.409%	$62.8727	$62.87	$62.85	$62.90
Purchase #2	$101.53	10.782%	$112.477	$112.48	$112.50	$112.50
Purchase #3	$46.45	6.427%	$49.4353	$49.44	$49.45	$49.40
Purchase #4	$17.29	9.352%	$18.907	$18.91	$18.90	$18.90
Purchase #5	$231.78	4.419%	$242.0224	$242.02	$242.00	$242.00
Purchase #6	$194.46	10.239%	$214.3708	$214.37	$214.35	$214.40
Purchase #7	$92.51	8.348%	$100.2327	$100.23	$100.25	$100.20
7 purchase totals =	$744.82		$800.3179	$800.32	$800.30	$800.30