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	$49.81	5.532%	$52.5655	$52.57	$52.55	$52.60
Purchase #2	$242.98	10.239%	$267.8587	$267.86	$267.85	$267.90
Purchase #3	$159.38	5.706%	$168.4742	$168.47	$168.45	$168.50
Purchase #4	$247.96	3.127%	$255.7137	$255.71	$255.70	$255.70
Purchase #5	$147.93	11.273%	$164.6061	$164.61	$164.60	$164.60
Purchase #6	$83.37	11.780%	$93.191	$93.19	$93.20	$93.20
Purchase #7	$234.82	8.631%	$255.0873	$255.09	$255.10	$255.10
7 purchase totals =	$1,166.25		$1,257.4965	$1,257.50	$1,257.45	$1,257.60