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	$59.29	6.155%	$62.9393	$62.94	$62.95	$62.90
Purchase #2	$9.59	13.332%	$10.8685	$10.87	$10.85	$10.90
Purchase #3	$223.58	6.752%	$238.6761	$238.68	$238.70	$238.70
Purchase #4	$123.83	12.874%	$139.7719	$139.77	$139.75	$139.80
Purchase #5	$214.61	6.385%	$228.3128	$228.31	$228.30	$228.30
Purchase #6	$51.49	6.864%	$55.0243	$55.02	$55.00	$55.00
Purchase #7	$250.93	4.756%	$262.8642	$262.86	$262.85	$262.90
7 purchase totals =	$933.32		$998.4571	$998.45	$998.40	$998.50