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 $195.30   4.234%   $203.569   $203.57   $203.55   $203.60  
  Purchase #2 $212.92   13.297%   $241.232   $241.23   $241.25   $241.20  
  Purchase #3 $103.61   6.311%   $110.1488   $110.15   $110.15   $110.10  
  Purchase #4 $184.70   4.844%   $193.6469   $193.65   $193.65   $193.60  
  Purchase #5 $13.74   9.611%   $15.0606   $15.06   $15.05   $15.10  
  Purchase #6 $182.61   4.758%   $191.2986   $191.30   $191.30   $191.30  
  Purchase #7 $91.47   13.775%   $104.07   $104.07   $104.05   $104.10  
  7 purchase totals = $984.35       $1,059.0259   $1,059.03   $1,059.00   $1,059.00