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 $58.49   6.322%   $62.1877   $62.19   $62.20   $62.20  
  Purchase #2 $233.41   12.103%   $261.6596   $261.66   $261.65   $261.70  
  Purchase #3 $53.78   10.438%   $59.3936   $59.39   $59.40   $59.40  
  Purchase #4 $25.96   13.273%   $29.4057   $29.41   $29.40   $29.40  
  Purchase #5 $216.79   11.200%   $241.0705   $241.07   $241.05   $241.10  
  Purchase #6 $131.58   9.484%   $144.059   $144.06   $144.05   $144.10  
  Purchase #7 $217.74   4.743%   $228.0674   $228.07   $228.05   $228.10  
  7 purchase totals = $937.75       $1,025.8435   $1,025.85   $1,025.80   $1,026.00