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 $163.69   6.744%   $174.7293   $174.73   $174.75   $174.70  
  Purchase #2 $94.47   3.271%   $97.5601   $97.56   $97.55   $97.60  
  Purchase #3 $51.41   6.696%   $54.8524   $54.85   $54.85   $54.90  
  Purchase #4 $245.51   4.850%   $257.4172   $257.42   $257.40   $257.40  
  Purchase #5 $85.26   11.397%   $94.9771   $94.98   $95.00   $95.00  
  Purchase #6 $192.28   8.482%   $208.5892   $208.59   $208.60   $208.60  
  Purchase #7 $249.69   7.636%   $268.7563   $268.76   $268.75   $268.80  
  7 purchase totals = $1,082.31       $1,156.8816   $1,156.89   $1,156.90   $1,157.00