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	$176.65	13.726%	$200.897	$200.90	$200.90	$200.90
Purchase #2	$109.82	12.450%	$123.4926	$123.49	$123.50	$123.50
Purchase #3	$185.80	13.507%	$210.896	$210.90	$210.90	$210.90
Purchase #4	$43.94	7.794%	$47.3647	$47.36	$47.35	$47.40
Purchase #5	$81.83	5.861%	$86.6261	$86.63	$86.65	$86.60
Purchase #6	$176.34	13.535%	$200.2076	$200.21	$200.20	$200.20
Purchase #7	$38.98	6.554%	$41.5347	$41.53	$41.55	$41.50
7 purchase totals =	$813.36		$911.0187	$911.02	$911.05	$911.00