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	$247.43	4.788%	$259.2769	$259.28	$259.30	$259.30
Purchase #2	$143.52	7.383%	$154.1161	$154.12	$154.10	$154.10
Purchase #3	$90.64	3.746%	$94.0354	$94.04	$94.05	$94.00
Purchase #4	$119.29	11.118%	$132.5527	$132.55	$132.55	$132.60
Purchase #5	$55.49	7.182%	$59.4753	$59.48	$59.50	$59.50
Purchase #6	$143.34	6.620%	$152.8291	$152.83	$152.85	$152.80
Purchase #7	$129.77	8.360%	$140.6188	$140.62	$140.60	$140.60
7 purchase totals =	$929.48		$992.9043	$992.92	$992.95	$992.90