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	$55.87	7.152%	$59.8658	$59.87	$59.85	$59.90
Purchase #2	$220.28	9.836%	$241.9467	$241.95	$241.95	$241.90
Purchase #3	$31.67	9.873%	$34.7968	$34.80	$34.80	$34.80
Purchase #4	$85.38	11.354%	$95.074	$95.07	$95.05	$95.10
Purchase #5	$122.57	7.300%	$131.5176	$131.52	$131.50	$131.50
Purchase #6	$52.51	12.665%	$59.1604	$59.16	$59.15	$59.20
Purchase #7	$97.96	12.779%	$110.4783	$110.48	$110.50	$110.50
7 purchase totals =	$666.24		$732.8396	$732.85	$732.80	$732.90