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 $51.69   4.359%   $53.9432   $53.94   $53.95   $53.90  
  Purchase #2 $180.73   8.104%   $195.3764   $195.38   $195.40   $195.40  
  Purchase #3 $200.95   3.865%   $208.7167   $208.72   $208.70   $208.70  
  Purchase #4 $60.96   3.838%   $63.2996   $63.30   $63.30   $63.30  
  Purchase #5 $246.40   13.265%   $279.085   $279.09   $279.10   $279.10  
  Purchase #6 $47.41   8.259%   $51.3256   $51.33   $51.35   $51.30  
  Purchase #7 $248.48   7.504%   $267.1259   $267.13   $267.15   $267.10  
  7 purchase totals = $1,036.62       $1,118.8724   $1,118.89   $1,118.95   $1,118.80