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 $68.68   9.460%   $75.1771   $75.18   $75.20   $75.20  
  Purchase #2 $248.55   7.588%   $267.41   $267.41   $267.40   $267.40  
  Purchase #3 $144.66   3.464%   $149.671   $149.67   $149.65   $149.70  
  Purchase #4 $119.83   9.327%   $131.0065   $131.01   $131.00   $131.00  
  Purchase #5 $141.97   10.795%   $157.2957   $157.30   $157.30   $157.30  
  Purchase #6 $197.30   13.473%   $223.8822   $223.88   $223.90   $223.90  
  Purchase #7 $56.63   10.845%   $62.7715   $62.77   $62.75   $62.80  
  7 purchase totals = $977.62       $1,067.2140   $1,067.22   $1,067.20   $1,067.30