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	$123.35	8.843%	$134.2578	$134.26	$134.25	$134.30
Purchase #2	$210.89	5.473%	$222.432	$222.43	$222.45	$222.40
Purchase #3	$126.96	7.541%	$136.5341	$136.53	$136.55	$136.50
Purchase #4	$86.97	3.257%	$89.8026	$89.80	$89.80	$89.80
Purchase #5	$75.97	3.678%	$78.7642	$78.76	$78.75	$78.80
Purchase #6	$137.45	7.732%	$148.0776	$148.08	$148.10	$148.10
Purchase #7	$218.94	13.798%	$249.1493	$249.15	$249.15	$249.10
7 purchase totals =	$980.53		$1,059.0176	$1,059.01	$1,059.05	$1,059.00