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 $21.84   8.625%   $23.7237   $23.72   $23.70   $23.70  
  Purchase #2 $104.93   8.550%   $113.9015   $113.90   $113.90   $113.90  
  Purchase #3 $177.65   13.308%   $201.2917   $201.29   $201.30   $201.30  
  Purchase #4 $203.63   5.419%   $214.6647   $214.66   $214.65   $214.70  
  Purchase #5 $95.69   9.295%   $104.5844   $104.58   $104.60   $104.60  
  Purchase #6 $230.98   9.662%   $253.2973   $253.30   $253.30   $253.30  
  Purchase #7 $250.40   9.125%   $273.249   $273.25   $273.25   $273.20  
  7 purchase totals = $1,085.12       $1,184.7123   $1,184.70   $1,184.70   $1,184.70