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 $196.54   7.382%   $211.0486   $211.05   $211.05   $211.00  
  Purchase #2 $203.56   13.414%   $230.8655   $230.87   $230.85   $230.90  
  Purchase #3 $7.93   7.615%   $8.5339   $8.53   $8.55   $8.50  
  Purchase #4 $93.93   7.855%   $101.3082   $101.31   $101.30   $101.30  
  Purchase #5 $128.25   7.699%   $138.124   $138.12   $138.10   $138.10  
  Purchase #6 $158.91   10.790%   $176.0564   $176.06   $176.05   $176.10  
  Purchase #7 $225.81   8.702%   $245.46   $245.46   $245.45   $245.50  
  7 purchase totals = $1,014.93       $1,111.3966   $1,111.40   $1,111.35   $1,111.40