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 $64.46   7.692%   $69.4183   $69.42   $69.40   $69.40  
  Purchase #2 $111.69   9.378%   $122.1643   $122.16   $122.15   $122.20  
  Purchase #3 $197.76   5.579%   $208.793   $208.79   $208.80   $208.80  
  Purchase #4 $242.33   9.714%   $265.8699   $265.87   $265.85   $265.90  
  Purchase #5 $144.63   11.423%   $161.1511   $161.15   $161.15   $161.20  
  Purchase #6 $24.93   13.196%   $28.2198   $28.22   $28.20   $28.20  
  Purchase #7 $219.67   9.132%   $239.7303   $239.73   $239.75   $239.70  
  7 purchase totals = $1,005.47       $1,095.3467   $1,095.34   $1,095.30   $1,095.40