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 $23.83   9.350%   $26.0581   $26.06   $26.05   $26.10  
  Purchase #2 $86.28   3.555%   $89.3473   $89.35   $89.35   $89.30  
  Purchase #3 $39.95   10.164%   $44.0105   $44.01   $44.00   $44.00  
  Purchase #4 $62.60   11.283%   $69.6632   $69.66   $69.65   $69.70  
  Purchase #5 $59.63   13.811%   $67.8655   $67.87   $67.85   $67.90  
  Purchase #6 $229.34   7.132%   $245.6965   $245.70   $245.70   $245.70  
  Purchase #7 $20.51   5.137%   $21.5636   $21.56   $21.55   $21.60  
  7 purchase totals = $522.14       $564.2047   $564.21   $564.15   $564.30