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 $125.41   7.278%   $134.5373   $134.54   $134.55   $134.50  
  Purchase #2 $78.72   4.142%   $81.9806   $81.98   $82.00   $82.00  
  Purchase #3 $197.66   4.493%   $206.5409   $206.54   $206.55   $206.50  
  Purchase #4 $88.85   12.779%   $100.2041   $100.20   $100.20   $100.20  
  Purchase #5 $186.86   11.575%   $208.489   $208.49   $208.50   $208.50  
  Purchase #6 $109.79   3.295%   $113.4076   $113.41   $113.40   $113.40  
  Purchase #7 $107.86   9.311%   $117.9028   $117.90   $117.90   $117.90  
  7 purchase totals = $895.15       $963.0623   $963.06   $963.10   $963.00