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 $59.81   5.548%   $63.1283   $63.13   $63.15   $63.10  
  Purchase #2 $201.83   4.394%   $210.6984   $210.70   $210.70   $210.70  
  Purchase #3 $25.71   12.302%   $28.8728   $28.87   $28.85   $28.90  
  Purchase #4 $241.73   5.232%   $254.3773   $254.38   $254.40   $254.40  
  Purchase #5 $130.97   5.154%   $137.7202   $137.72   $137.70   $137.70  
  Purchase #6 $213.35   3.517%   $220.8535   $220.85   $220.85   $220.90  
  Purchase #7 $179.75   10.787%   $199.1396   $199.14   $199.15   $199.10  
  7 purchase totals = $1,053.15       $1,114.7901   $1,114.79   $1,114.80   $1,114.80