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	$200.59	7.566%	$215.7666	$215.77	$215.75	$215.80
Purchase #2	$25.94	6.332%	$27.5825	$27.58	$27.60	$27.60
Purchase #3	$14.40	9.811%	$15.8128	$15.81	$15.80	$15.80
Purchase #4	$133.31	4.340%	$139.0957	$139.10	$139.10	$139.10
Purchase #5	$77.28	10.514%	$85.4052	$85.41	$85.40	$85.40
Purchase #6	$125.41	13.301%	$142.0908	$142.09	$142.10	$142.10
Purchase #7	$155.48	10.304%	$171.5007	$171.50	$171.50	$171.50
7 purchase totals =	$732.41		$797.2543	$797.26	$797.25	$797.30