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 $23.70   5.613%   $25.0303   $25.03   $25.05   $25.00  
  Purchase #2 $56.26   10.167%   $61.98   $61.98   $62.00   $62.00  
  Purchase #3 $177.49   5.187%   $186.6964   $186.70   $186.70   $186.70  
  Purchase #4 $175.70   9.589%   $192.5479   $192.55   $192.55   $192.50  
  Purchase #5 $158.32   3.636%   $164.0765   $164.08   $164.10   $164.10  
  Purchase #6 $217.55   8.574%   $236.2027   $236.20   $236.20   $236.20  
  Purchase #7 $179.38   7.779%   $193.334   $193.33   $193.35   $193.30  
  7 purchase totals = $988.40       $1,059.8678   $1,059.87   $1,059.95   $1,059.80