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 $73.54   11.815%   $82.2288   $82.23   $82.25   $82.20  
  Purchase #2 $237.36   3.618%   $245.9477   $245.95   $245.95   $245.90  
  Purchase #3 $74.79   11.183%   $83.1538   $83.15   $83.15   $83.20  
  Purchase #4 $207.97   11.648%   $232.1943   $232.19   $232.20   $232.20  
  Purchase #5 $57.58   10.676%   $63.7272   $63.73   $63.75   $63.70  
  Purchase #6 $156.61   11.869%   $175.198   $175.20   $175.20   $175.20  
  Purchase #7 $188.45   6.258%   $200.2432   $200.24   $200.25   $200.20  
  7 purchase totals = $996.30       $1,082.6930   $1,082.69   $1,082.75   $1,082.60