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	$103.94	9.737%	$114.0606	$114.06	$114.05	$114.10
Purchase #2	$174.33	7.757%	$187.8528	$187.85	$187.85	$187.90
Purchase #3	$119.78	4.153%	$124.7545	$124.75	$124.75	$124.80
Purchase #4	$231.90	10.403%	$256.0246	$256.02	$256.00	$256.00
Purchase #5	$18.49	10.551%	$20.4409	$20.44	$20.45	$20.40
Purchase #6	$240.50	7.664%	$258.9319	$258.93	$258.95	$258.90
Purchase #7	$168.52	7.328%	$180.8691	$180.87	$180.85	$180.90
7 purchase totals =	$1,057.46		$1,142.9344	$1,142.92	$1,142.90	$1,143.00