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 $214.67   8.355%   $232.6057   $232.61   $232.60   $232.60  
  Purchase #2 $249.31   4.455%   $260.4168   $260.42   $260.40   $260.40  
  Purchase #3 $59.44   12.426%   $66.826   $66.83   $66.85   $66.80  
  Purchase #4 $9.47   11.544%   $10.5632   $10.56   $10.55   $10.60  
  Purchase #5 $32.94   11.253%   $36.6467   $36.65   $36.65   $36.60  
  Purchase #6 $156.80   11.746%   $175.2177   $175.22   $175.20   $175.20  
  Purchase #7 $227.73   8.411%   $246.8844   $246.88   $246.90   $246.90  
  7 purchase totals = $950.36       $1,029.1605   $1,029.17   $1,029.15   $1,029.10