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 $114.71   9.665%   $125.7967   $125.80   $125.80   $125.80  
  Purchase #2 $52.54   11.397%   $58.528   $58.53   $58.55   $58.50  
  Purchase #3 $212.43   5.642%   $224.4153   $224.42   $224.40   $224.40  
  Purchase #4 $79.85   3.571%   $82.7014   $82.70   $82.70   $82.70  
  Purchase #5 $87.51   6.839%   $93.4948   $93.49   $93.50   $93.50  
  Purchase #6 $215.74   6.683%   $230.1579   $230.16   $230.15   $230.20  
  Purchase #7 $215.87   13.432%   $244.8657   $244.87   $244.85   $244.90  
  7 purchase totals = $978.65       $1,059.9598   $1,059.97   $1,059.95   $1,060.00