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 $54.76   13.267%   $62.025   $62.03   $62.05   $62.00  
  Purchase #2 $170.75   8.387%   $185.0708   $185.07   $185.05   $185.10  
  Purchase #3 $217.46   10.633%   $240.5825   $240.58   $240.60   $240.60  
  Purchase #4 $135.37   4.512%   $141.4779   $141.48   $141.50   $141.50  
  Purchase #5 $104.41   5.713%   $110.3749   $110.37   $110.35   $110.40  
  Purchase #6 $155.36   10.347%   $171.4351   $171.44   $171.45   $171.40  
  Purchase #7 $239.82   5.343%   $252.6336   $252.63   $252.65   $252.60  
  7 purchase totals = $1,077.93       $1,163.5998   $1,163.60   $1,163.65   $1,163.60