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 $201.46   4.267%   $210.0563   $210.06   $210.05   $210.10  
  Purchase #2 $64.89   3.121%   $66.9152   $66.92   $66.90   $66.90  
  Purchase #3 $7.73   6.489%   $8.2316   $8.23   $8.25   $8.20  
  Purchase #4 $58.57   8.430%   $63.5075   $63.51   $63.50   $63.50  
  Purchase #5 $217.51   11.623%   $242.7912   $242.79   $242.80   $242.80  
  Purchase #6 $250.84   4.801%   $262.8828   $262.88   $262.90   $262.90  
  Purchase #7 $231.32   11.797%   $258.6088   $258.61   $258.60   $258.60  
  7 purchase totals = $1,032.32       $1,112.9934   $1,113.00   $1,113.00   $1,113.00