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 $60.53   3.537%   $62.6709   $62.67   $62.65   $62.70  
  Purchase #2 $222.97   10.769%   $246.9816   $246.98   $247.00   $247.00  
  Purchase #3 $130.73   11.686%   $146.0071   $146.01   $146.00   $146.00  
  Purchase #4 $127.68   11.782%   $142.7233   $142.72   $142.70   $142.70  
  Purchase #5 $225.81   13.293%   $255.8269   $255.83   $255.85   $255.80  
  Purchase #6 $159.46   8.524%   $173.0524   $173.05   $173.05   $173.10  
  Purchase #7 $131.28   9.706%   $144.022   $144.02   $144.00   $144.00  
  7 purchase totals = $1,058.46       $1,171.2842   $1,171.28   $1,171.25   $1,171.30