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 $125.42   5.425%   $132.224   $132.22   $132.20   $132.20  
  Purchase #2 $136.56   7.349%   $146.5958   $146.60   $146.60   $146.60  
  Purchase #3 $67.39   8.340%   $73.0103   $73.01   $73.00   $73.00  
  Purchase #4 $57.29   9.445%   $62.701   $62.70   $62.70   $62.70  
  Purchase #5 $201.47   6.824%   $215.2183   $215.22   $215.20   $215.20  
  Purchase #6 $90.96   8.410%   $98.6097   $98.61   $98.60   $98.60  
  Purchase #7 $187.44   13.491%   $212.7275   $212.73   $212.75   $212.70  
  7 purchase totals = $866.53       $941.0866   $941.09   $941.05   $941.00