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 $213.70   8.870%   $232.6552   $232.66   $232.65   $232.70  
  Purchase #2 $230.55   5.255%   $242.6654   $242.67   $242.65   $242.70  
  Purchase #3 $49.86   8.419%   $54.0577   $54.06   $54.05   $54.10  
  Purchase #4 $137.47   3.663%   $142.5055   $142.51   $142.50   $142.50  
  Purchase #5 $87.52   10.507%   $96.7157   $96.72   $96.70   $96.70  
  Purchase #6 $12.89   5.563%   $13.6071   $13.61   $13.60   $13.60  
  Purchase #7 $214.71   4.650%   $224.694   $224.69   $224.70   $224.70  
  7 purchase totals = $946.70       $1,006.9006   $1,006.92   $1,006.85   $1,007.00