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 $161.65   8.870%   $175.9884   $175.99   $176.00   $176.00  
  Purchase #2 $76.62   3.693%   $79.4496   $79.45   $79.45   $79.40  
  Purchase #3 $214.54   5.200%   $225.6961   $225.70   $225.70   $225.70  
  Purchase #4 $95.40   9.652%   $104.608   $104.61   $104.60   $104.60  
  Purchase #5 $211.28   11.268%   $235.087   $235.09   $235.10   $235.10  
  Purchase #6 $249.31   9.740%   $273.5928   $273.59   $273.60   $273.60  
  Purchase #7 $56.53   11.403%   $62.9761   $62.98   $63.00   $63.00  
  7 purchase totals = $1,065.33       $1,157.3980   $1,157.41   $1,157.45   $1,157.40