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 $59.35   10.669%   $65.6821   $65.68   $65.70   $65.70  
  Purchase #2 $16.33   8.253%   $17.6777   $17.68   $17.70   $17.70  
  Purchase #3 $175.36   3.613%   $181.6958   $181.70   $181.70   $181.70  
  Purchase #4 $83.27   13.766%   $94.7329   $94.73   $94.75   $94.70  
  Purchase #5 $86.86   13.868%   $98.9057   $98.91   $98.90   $98.90  
  Purchase #6 $51.56   12.739%   $58.1282   $58.13   $58.15   $58.10  
  Purchase #7 $199.48   8.562%   $216.5595   $216.56   $216.55   $216.60  
  7 purchase totals = $672.21       $733.3819   $733.39   $733.45   $733.40