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 $90.65   3.385%   $93.7185   $93.72   $93.70   $93.70  
  Purchase #2 $247.40   5.767%   $261.6676   $261.67   $261.65   $261.70  
  Purchase #3 $81.53   11.551%   $90.9475   $90.95   $90.95   $90.90  
  Purchase #4 $96.85   10.608%   $107.1238   $107.12   $107.10   $107.10  
  Purchase #5 $41.43   13.854%   $47.1697   $47.17   $47.15   $47.20  
  Purchase #6 $166.51   9.624%   $182.5349   $182.53   $182.55   $182.50  
  Purchase #7 $152.64   9.347%   $166.9073   $166.91   $166.90   $166.90  
  7 purchase totals = $877.01       $950.0693   $950.07   $950.00   $950.00