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 $105.97   7.370%   $113.78   $113.78   $113.80   $113.80  
  Purchase #2 $93.42   5.281%   $98.3535   $98.35   $98.35   $98.40  
  Purchase #3 $126.72   6.372%   $134.7946   $134.79   $134.80   $134.80  
  Purchase #4 $143.75   7.552%   $154.606   $154.61   $154.60   $154.60  
  Purchase #5 $114.26   6.740%   $121.9611   $121.96   $121.95   $122.00  
  Purchase #6 $133.66   6.165%   $141.9001   $141.90   $141.90   $141.90  
  Purchase #7 $237.39   9.541%   $260.0394   $260.04   $260.05   $260.00  
  7 purchase totals = $955.17       $1,025.4347   $1,025.43   $1,025.45   $1,025.50