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 $95.65   3.320%   $98.8256   $98.83   $98.85   $98.80  
  Purchase #2 $246.50   6.186%   $261.7485   $261.75   $261.75   $261.70  
  Purchase #3 $32.75   12.372%   $36.8018   $36.80   $36.80   $36.80  
  Purchase #4 $146.56   12.706%   $165.1819   $165.18   $165.20   $165.20  
  Purchase #5 $215.36   9.365%   $235.5285   $235.53   $235.55   $235.50  
  Purchase #6 $17.57   4.378%   $18.3392   $18.34   $18.35   $18.30  
  Purchase #7 $48.68   4.604%   $50.9212   $50.92   $50.90   $50.90  
  7 purchase totals = $803.07       $867.3467   $867.35   $867.40   $867.20