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 $68.38   12.554%   $76.9644   $76.96   $76.95   $77.00  
  Purchase #2 $196.59   8.256%   $212.8205   $212.82   $212.80   $212.80  
  Purchase #3 $145.95   3.643%   $151.267   $151.27   $151.25   $151.30  
  Purchase #4 $58.93   10.454%   $65.0905   $65.09   $65.10   $65.10  
  Purchase #5 $174.57   4.676%   $182.7329   $182.73   $182.75   $182.70  
  Purchase #6 $233.75   7.869%   $252.1438   $252.14   $252.15   $252.10  
  Purchase #7 $11.26   6.112%   $11.9482   $11.95   $11.95   $11.90  
  7 purchase totals = $889.43       $952.9673   $952.96   $952.95   $952.90