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 $56.67   9.485%   $62.0451   $62.05   $62.05   $62.00  
  Purchase #2 $122.55   11.189%   $136.2621   $136.26   $136.25   $136.30  
  Purchase #3 $228.55   4.607%   $239.0793   $239.08   $239.10   $239.10  
  Purchase #4 $27.67   9.618%   $30.3313   $30.33   $30.35   $30.30  
  Purchase #5 $249.94   8.687%   $271.6523   $271.65   $271.65   $271.70  
  Purchase #6 $180.69   8.476%   $196.0053   $196.01   $196.00   $196.00  
  Purchase #7 $97.65   11.785%   $109.1581   $109.16   $109.15   $109.20  
  7 purchase totals = $963.72       $1,044.5335   $1,044.54   $1,044.55   $1,044.60