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	$144.58	11.334%	$160.9667	$160.97	$160.95	$161.00
Purchase #2	$29.52	11.315%	$32.8602	$32.86	$32.85	$32.90
Purchase #3	$180.75	11.124%	$200.8566	$200.86	$200.85	$200.90
Purchase #4	$86.46	12.641%	$97.3894	$97.39	$97.40	$97.40
Purchase #5	$19.52	7.692%	$21.0215	$21.02	$21.00	$21.00
Purchase #6	$45.32	7.731%	$48.8237	$48.82	$48.80	$48.80
Purchase #7	$94.77	11.714%	$105.8714	$105.87	$105.85	$105.90
7 purchase totals =	$600.92		$667.7895	$667.79	$667.70	$667.90