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 $61.63   5.750%   $65.1737   $65.17   $65.15   $65.20  
  Purchase #2 $174.48   11.675%   $194.8505   $194.85   $194.85   $194.90  
  Purchase #3 $155.56   8.544%   $168.851   $168.85   $168.85   $168.90  
  Purchase #4 $250.26   12.434%   $281.3773   $281.38   $281.40   $281.40  
  Purchase #5 $113.84   12.615%   $128.2009   $128.20   $128.20   $128.20  
  Purchase #6 $206.53   6.570%   $220.099   $220.10   $220.10   $220.10  
  Purchase #7 $125.95   12.226%   $141.3486   $141.35   $141.35   $141.30  
  7 purchase totals = $1,088.25       $1,199.9010   $1,199.90   $1,199.90   $1,200.00