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 $186.67   8.565%   $202.6583   $202.66   $202.65   $202.70  
  Purchase #2 $182.95   12.711%   $206.2048   $206.20   $206.20   $206.20  
  Purchase #3 $201.84   3.359%   $208.6198   $208.62   $208.60   $208.60  
  Purchase #4 $224.48   9.361%   $245.4936   $245.49   $245.50   $245.50  
  Purchase #5 $98.55   9.274%   $107.6895   $107.69   $107.70   $107.70  
  Purchase #6 $22.81   7.510%   $24.523   $24.52   $24.50   $24.50  
  Purchase #7 $10.28   8.209%   $11.1239   $11.12   $11.10   $11.10  
  7 purchase totals = $927.58       $1,006.3129   $1,006.30   $1,006.25   $1,006.30