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 $231.25   6.227%   $245.6499   $245.65   $245.65   $245.60  
  Purchase #2 $31.88   8.201%   $34.4945   $34.49   $34.50   $34.50  
  Purchase #3 $190.72   5.460%   $201.1333   $201.13   $201.15   $201.10  
  Purchase #4 $216.58   8.821%   $235.6845   $235.68   $235.70   $235.70  
  Purchase #5 $227.27   8.512%   $246.6152   $246.62   $246.60   $246.60  
  Purchase #6 $249.93   7.268%   $268.0949   $268.09   $268.10   $268.10  
  Purchase #7 $203.51   13.858%   $231.7124   $231.71   $231.70   $231.70  
  7 purchase totals = $1,351.14       $1,463.3847   $1,463.37   $1,463.40   $1,463.30