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 $214.62   11.697%   $239.7241   $239.72   $239.70   $239.70  
  Purchase #2 $217.41   8.550%   $235.9986   $236.00   $236.00   $236.00  
  Purchase #3 $12.34   13.317%   $13.9833   $13.98   $14.00   $14.00  
  Purchase #4 $36.60   13.642%   $41.593   $41.59   $41.60   $41.60  
  Purchase #5 $136.27   3.485%   $141.019   $141.02   $141.00   $141.00  
  Purchase #6 $212.90   5.667%   $224.965   $224.97   $224.95   $225.00  
  Purchase #7 $158.89   10.683%   $175.8642   $175.86   $175.85   $175.90  
  7 purchase totals = $989.03       $1,073.1472   $1,073.14   $1,073.10   $1,073.20