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 $85.95   7.683%   $92.5535   $92.55   $92.55   $92.60  
  Purchase #2 $102.84   11.464%   $114.6296   $114.63   $114.65   $114.60  
  Purchase #3 $168.35   3.710%   $174.5958   $174.60   $174.60   $174.60  
  Purchase #4 $69.33   3.327%   $71.6366   $71.64   $71.65   $71.60  
  Purchase #5 $205.73   5.811%   $217.685   $217.69   $217.70   $217.70  
  Purchase #6 $63.59   4.277%   $66.3097   $66.31   $66.30   $66.30  
  Purchase #7 $34.30   8.188%   $37.1085   $37.11   $37.10   $37.10  
  7 purchase totals = $730.09       $774.5187   $774.53   $774.55   $774.50