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	$54.33	9.405%	$59.4397	$59.44	$59.45	$59.40
Purchase #2	$38.39	11.140%	$42.6666	$42.67	$42.65	$42.70
Purchase #3	$178.90	13.665%	$203.3467	$203.35	$203.35	$203.30
Purchase #4	$112.70	6.395%	$119.9072	$119.91	$119.90	$119.90
Purchase #5	$233.94	10.237%	$257.8884	$257.89	$257.90	$257.90
Purchase #6	$196.82	5.865%	$208.3635	$208.36	$208.35	$208.40
Purchase #7	$108.43	8.732%	$117.8981	$117.90	$117.90	$117.90
7 purchase totals =	$923.51		$1,009.5102	$1,009.52	$1,009.50	$1,009.50