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 $241.53   8.510%   $262.0842   $262.08   $262.10   $262.10  
  Purchase #2 $180.72   11.270%   $201.0871   $201.09   $201.10   $201.10  
  Purchase #3 $234.40   3.855%   $243.4361   $243.44   $243.45   $243.40  
  Purchase #4 $182.88   4.135%   $190.4421   $190.44   $190.45   $190.40  
  Purchase #5 $201.89   5.780%   $213.5592   $213.56   $213.55   $213.60  
  Purchase #6 $140.64   11.192%   $156.3804   $156.38   $156.40   $156.40  
  Purchase #7 $185.46   6.200%   $196.9585   $196.96   $196.95   $197.00  
  7 purchase totals = $1,367.52       $1,463.9476   $1,463.95   $1,464.00   $1,464.00