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 $119.73   5.157%   $125.9045   $125.90   $125.90   $125.90  
  Purchase #2 $138.73   7.498%   $149.132   $149.13   $149.15   $149.10  
  Purchase #3 $56.61   8.540%   $61.4445   $61.44   $61.45   $61.40  
  Purchase #4 $78.59   6.204%   $83.4657   $83.47   $83.45   $83.50  
  Purchase #5 $238.53   9.450%   $261.0711   $261.07   $261.05   $261.10  
  Purchase #6 $101.68   11.784%   $113.662   $113.66   $113.65   $113.70  
  Purchase #7 $224.75   3.358%   $232.2971   $232.30   $232.30   $232.30  
  7 purchase totals = $958.62       $1,026.9769   $1,026.97   $1,026.95   $1,027.00