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 $67.45   5.265%   $71.0012   $71.00   $71.00   $71.00  
  Purchase #2 $235.31   10.205%   $259.3234   $259.32   $259.30   $259.30  
  Purchase #3 $33.80   12.666%   $38.0811   $38.08   $38.10   $38.10  
  Purchase #4 $57.54   4.689%   $60.2381   $60.24   $60.25   $60.20  
  Purchase #5 $34.38   4.769%   $36.0196   $36.02   $36.00   $36.00  
  Purchase #6 $8.89   5.576%   $9.3857   $9.39   $9.40   $9.40  
  Purchase #7 $237.94   8.695%   $258.6289   $258.63   $258.65   $258.60  
  7 purchase totals = $675.31       $732.6780   $732.68   $732.70   $732.60