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 $56.96   11.595%   $63.5645   $63.56   $63.55   $63.60  
  Purchase #2 $208.36   3.444%   $215.5359   $215.54   $215.55   $215.50  
  Purchase #3 $237.51   13.138%   $268.7141   $268.71   $268.70   $268.70  
  Purchase #4 $245.58   5.309%   $258.6178   $258.62   $258.60   $258.60  
  Purchase #5 $133.31   3.733%   $138.2865   $138.29   $138.30   $138.30  
  Purchase #6 $234.62   12.302%   $263.483   $263.48   $263.50   $263.50  
  Purchase #7 $236.74   7.504%   $254.505   $254.51   $254.50   $254.50  
  7 purchase totals = $1,353.08       $1,462.7068   $1,462.71   $1,462.70   $1,462.70