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	$118.78	10.390%	$131.1212	$131.12	$131.10	$131.10
Purchase #2	$142.47	7.267%	$152.8233	$152.82	$152.80	$152.80
Purchase #3	$47.73	8.531%	$51.8018	$51.80	$51.80	$51.80
Purchase #4	$146.55	5.568%	$154.7099	$154.71	$154.70	$154.70
Purchase #5	$56.47	7.227%	$60.5511	$60.55	$60.55	$60.60
Purchase #6	$237.73	11.536%	$265.1545	$265.15	$265.15	$265.20
Purchase #7	$100.89	11.747%	$112.7415	$112.74	$112.75	$112.70
7 purchase totals =	$850.62		$928.9033	$928.89	$928.85	$928.90