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 $98.47   9.612%   $107.9349   $107.93   $107.95   $107.90  
  Purchase #2 $196.72   3.189%   $202.9934   $202.99   $203.00   $203.00  
  Purchase #3 $58.90   11.318%   $65.5663   $65.57   $65.55   $65.60  
  Purchase #4 $47.86   11.428%   $53.3294   $53.33   $53.35   $53.30  
  Purchase #5 $215.73   13.407%   $244.6529   $244.65   $244.65   $244.70  
  Purchase #6 $248.46   5.209%   $261.4023   $261.40   $261.40   $261.40  
  Purchase #7 $231.37   6.685%   $246.8371   $246.84   $246.85   $246.80  
  7 purchase totals = $1,097.51       $1,182.7163   $1,182.71   $1,182.75   $1,182.70