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 $222.49   5.471%   $234.6624   $234.66   $234.65   $234.70  
  Purchase #2 $232.64   5.329%   $245.0374   $245.04   $245.05   $245.00  
  Purchase #3 $21.53   13.747%   $24.4897   $24.49   $24.50   $24.50  
  Purchase #4 $166.72   7.540%   $179.2907   $179.29   $179.30   $179.30  
  Purchase #5 $247.25   10.321%   $272.7687   $272.77   $272.75   $272.80  
  Purchase #6 $58.79   8.776%   $63.9494   $63.95   $63.95   $63.90  
  Purchase #7 $78.63   4.583%   $82.2336   $82.23   $82.25   $82.20  
  7 purchase totals = $1,028.05       $1,102.4319   $1,102.43   $1,102.45   $1,102.40