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 $59.47   3.592%   $61.6062   $61.61   $61.60   $61.60  
  Purchase #2 $30.80   6.118%   $32.6843   $32.68   $32.70   $32.70  
  Purchase #3 $214.78   5.199%   $225.9464   $225.95   $225.95   $225.90  
  Purchase #4 $41.69   13.250%   $47.2139   $47.21   $47.20   $47.20  
  Purchase #5 $162.95   11.480%   $181.6567   $181.66   $181.65   $181.70  
  Purchase #6 $104.94   9.232%   $114.6281   $114.63   $114.65   $114.60  
  Purchase #7 $57.89   6.349%   $61.5654   $61.57   $61.55   $61.60  
  7 purchase totals = $672.52       $725.3010   $725.31   $725.30   $725.30