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	$143.37	5.263%	$150.9156	$150.92	$150.90	$150.90
Purchase #2	$37.72	8.324%	$40.8598	$40.86	$40.85	$40.90
Purchase #3	$122.60	9.311%	$134.0153	$134.02	$134.00	$134.00
Purchase #4	$173.81	7.527%	$186.8927	$186.89	$186.90	$186.90
Purchase #5	$196.94	8.868%	$214.4046	$214.40	$214.40	$214.40
Purchase #6	$40.65	9.356%	$44.4532	$44.45	$44.45	$44.50
Purchase #7	$6.78	13.758%	$7.7128	$7.71	$7.70	$7.70
7 purchase totals =	$721.87		$779.2540	$779.25	$779.20	$779.30