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	$82.27	5.557%	$86.8417	$86.84	$86.85	$86.80
Purchase #2	$92.53	11.156%	$102.8526	$102.85	$102.85	$102.90
Purchase #3	$116.73	12.260%	$131.0411	$131.04	$131.05	$131.00
Purchase #4	$170.86	6.232%	$181.508	$181.51	$181.50	$181.50
Purchase #5	$142.54	12.443%	$160.2763	$160.28	$160.30	$160.30
Purchase #6	$119.82	13.577%	$136.088	$136.09	$136.10	$136.10
Purchase #7	$166.85	5.231%	$175.5779	$175.58	$175.60	$175.60
7 purchase totals =	$891.60		$974.1856	$974.19	$974.25	$974.20