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 $110.71   10.775%   $122.639   $122.64   $122.65   $122.60  
  Purchase #2 $119.62   5.164%   $125.7972   $125.80   $125.80   $125.80  
  Purchase #3 $43.60   9.721%   $47.8384   $47.84   $47.85   $47.80  
  Purchase #4 $250.34   12.407%   $281.3997   $281.40   $281.40   $281.40  
  Purchase #5 $39.53   3.443%   $40.891   $40.89   $40.90   $40.90  
  Purchase #6 $164.40   9.868%   $180.623   $180.62   $180.60   $180.60  
  Purchase #7 $204.59   10.787%   $226.6591   $226.66   $226.65   $226.70  
  7 purchase totals = $932.79       $1,025.8474   $1,025.85   $1,025.85   $1,025.80