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 $218.46   3.381%   $225.8461   $225.85   $225.85   $225.80  
  Purchase #2 $56.61   7.199%   $60.6854   $60.69   $60.70   $60.70  
  Purchase #3 $63.86   3.529%   $66.1136   $66.11   $66.10   $66.10  
  Purchase #4 $236.62   4.684%   $247.7033   $247.70   $247.70   $247.70  
  Purchase #5 $28.27   9.395%   $30.926   $30.93   $30.95   $30.90  
  Purchase #6 $33.94   4.398%   $35.4327   $35.43   $35.45   $35.40  
  Purchase #7 $58.72   11.491%   $65.4675   $65.47   $65.45   $65.50  
  7 purchase totals = $696.48       $732.1746   $732.18   $732.20   $732.10