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 $54.32   11.550%   $60.594   $60.59   $60.60   $60.60  
  Purchase #2 $241.30   9.414%   $264.016   $264.02   $264.00   $264.00  
  Purchase #3 $226.57   4.695%   $237.2075   $237.21   $237.20   $237.20  
  Purchase #4 $65.51   9.611%   $71.8062   $71.81   $71.80   $71.80  
  Purchase #5 $108.72   5.553%   $114.7572   $114.76   $114.75   $114.80  
  Purchase #6 $196.69   6.797%   $210.059   $210.06   $210.05   $210.10  
  Purchase #7 $73.86   3.197%   $76.2213   $76.22   $76.20   $76.20  
  7 purchase totals = $966.97       $1,034.6612   $1,034.67   $1,034.60   $1,034.70