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	$59.34	4.689%	$62.1225	$62.12	$62.10	$62.10
Purchase #2	$132.42	5.337%	$139.4873	$139.49	$139.50	$139.50
Purchase #3	$82.81	3.238%	$85.4914	$85.49	$85.50	$85.50
Purchase #4	$154.84	5.811%	$163.8378	$163.84	$163.85	$163.80
Purchase #5	$153.90	11.247%	$171.2091	$171.21	$171.20	$171.20
Purchase #6	$65.43	9.187%	$71.4411	$71.44	$71.45	$71.40
Purchase #7	$62.29	8.654%	$67.6806	$67.68	$67.70	$67.70
7 purchase totals =	$711.03		$761.2698	$761.27	$761.30	$761.20