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 $43.53   9.644%   $47.728   $47.73   $47.75   $47.70  
  Purchase #2 $56.48   12.765%   $63.6897   $63.69   $63.70   $63.70  
  Purchase #3 $144.67   3.411%   $149.6047   $149.60   $149.60   $149.60  
  Purchase #4 $207.81   9.601%   $227.7618   $227.76   $227.75   $227.80  
  Purchase #5 $192.69   5.311%   $202.9238   $202.92   $202.90   $202.90  
  Purchase #6 $209.47   9.438%   $229.2398   $229.24   $229.25   $229.20  
  Purchase #7 $38.84   5.778%   $41.0842   $41.08   $41.10   $41.10  
  7 purchase totals = $893.49       $962.0320   $962.02   $962.05   $962.00