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	$68.90	5.222%	$72.498	$72.50	$72.50	$72.50
Purchase #2	$40.62	5.789%	$42.9715	$42.97	$42.95	$43.00
Purchase #3	$121.56	10.874%	$134.7784	$134.78	$134.80	$134.80
Purchase #4	$83.79	3.705%	$86.8944	$86.89	$86.90	$86.90
Purchase #5	$172.51	13.801%	$196.3181	$196.32	$196.30	$196.30
Purchase #6	$120.93	13.691%	$137.4865	$137.49	$137.50	$137.50
Purchase #7	$160.28	11.455%	$178.6401	$178.64	$178.65	$178.60
7 purchase totals =	$768.59		$849.5870	$849.59	$849.60	$849.60