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 $201.47   5.151%   $211.8477   $211.85   $211.85   $211.80  
  Purchase #2 $247.27   4.786%   $259.1043   $259.10   $259.10   $259.10  
  Purchase #3 $14.85   12.729%   $16.7403   $16.74   $16.75   $16.70  
  Purchase #4 $147.96   12.164%   $165.9579   $165.96   $165.95   $166.00  
  Purchase #5 $79.99   6.713%   $85.3597   $85.36   $85.35   $85.40  
  Purchase #6 $125.81   4.767%   $131.8074   $131.81   $131.80   $131.80  
  Purchase #7 $250.41   8.175%   $270.881   $270.88   $270.90   $270.90  
  7 purchase totals = $1,067.76       $1,141.6983   $1,141.70   $1,141.70   $1,141.70