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 $68.25   12.222%   $76.5915   $76.59   $76.60   $76.60  
  Purchase #2 $61.32   12.802%   $69.1702   $69.17   $69.15   $69.20  
  Purchase #3 $224.80   12.783%   $253.5362   $253.54   $253.55   $253.50  
  Purchase #4 $119.79   8.284%   $129.7134   $129.71   $129.70   $129.70  
  Purchase #5 $238.46   12.786%   $268.9495   $268.95   $268.95   $268.90  
  Purchase #6 $217.42   8.531%   $235.9681   $235.97   $235.95   $236.00  
  Purchase #7 $13.47   12.821%   $15.197   $15.20   $15.20   $15.20  
  7 purchase totals = $943.51       $1,049.1259   $1,049.13   $1,049.10   $1,049.10