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 $62.35   5.417%   $65.7275   $65.73   $65.75   $65.70  
  Purchase #2 $228.88   10.754%   $253.4938   $253.49   $253.50   $253.50  
  Purchase #3 $55.90   8.514%   $60.6593   $60.66   $60.65   $60.70  
  Purchase #4 $203.41   8.312%   $220.3174   $220.32   $220.30   $220.30  
  Purchase #5 $65.29   9.218%   $71.3084   $71.31   $71.30   $71.30  
  Purchase #6 $230.69   3.124%   $237.8968   $237.90   $237.90   $237.90  
  Purchase #7 $46.56   5.611%   $49.1725   $49.17   $49.15   $49.20  
  7 purchase totals = $893.08       $958.5757   $958.58   $958.55   $958.60