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 $206.75   13.693%   $235.0603   $235.06   $235.05   $235.10  
  Purchase #2 $136.28   5.269%   $143.4606   $143.46   $143.45   $143.50  
  Purchase #3 $217.90   9.512%   $238.6266   $238.63   $238.65   $238.60  
  Purchase #4 $7.87   8.764%   $8.5597   $8.56   $8.55   $8.60  
  Purchase #5 $125.96   12.480%   $141.6798   $141.68   $141.70   $141.70  
  Purchase #6 $220.29   7.511%   $236.836   $236.84   $236.85   $236.80  
  Purchase #7 $145.28   12.682%   $163.7044   $163.70   $163.70   $163.70  
  7 purchase totals = $1,060.33       $1,167.9274   $1,167.93   $1,167.95   $1,168.00