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	$160.90	4.512%	$168.1598	$168.16	$168.15	$168.20
Purchase #2	$85.85	4.666%	$89.8558	$89.86	$89.85	$89.90
Purchase #3	$144.47	12.371%	$162.3424	$162.34	$162.35	$162.30
Purchase #4	$21.93	12.547%	$24.6816	$24.68	$24.70	$24.70
Purchase #5	$214.83	10.298%	$236.9532	$236.95	$236.95	$237.00
Purchase #6	$137.38	3.383%	$142.0276	$142.03	$142.05	$142.00
Purchase #7	$51.55	11.405%	$57.4293	$57.43	$57.45	$57.40
7 purchase totals =	$816.91		$881.4497	$881.45	$881.50	$881.50