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 $56.59   11.264%   $62.9643   $62.96   $62.95   $63.00  
  Purchase #2 $148.85   3.596%   $154.2026   $154.20   $154.20   $154.20  
  Purchase #3 $131.79   4.615%   $137.8721   $137.87   $137.85   $137.90  
  Purchase #4 $55.38   11.378%   $61.6811   $61.68   $61.70   $61.70  
  Purchase #5 $232.81   11.704%   $260.0581   $260.06   $260.05   $260.10  
  Purchase #6 $198.77   6.342%   $211.376   $211.38   $211.40   $211.40  
  Purchase #7 $237.48   3.412%   $245.5828   $245.58   $245.60   $245.60  
  7 purchase totals = $1,061.67       $1,133.7370   $1,133.73   $1,133.75   $1,133.90