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 $86.64   5.806%   $91.6703   $91.67   $91.65   $91.70  
  Purchase #2 $85.95   11.724%   $96.0268   $96.03   $96.05   $96.00  
  Purchase #3 $175.91   10.652%   $194.6479   $194.65   $194.65   $194.60  
  Purchase #4 $62.81   4.291%   $65.5052   $65.51   $65.50   $65.50  
  Purchase #5 $207.85   8.533%   $225.5858   $225.59   $225.60   $225.60  
  Purchase #6 $55.82   5.778%   $59.0453   $59.05   $59.05   $59.00  
  Purchase #7 $26.87   8.572%   $29.1733   $29.17   $29.15   $29.20  
  7 purchase totals = $701.85       $761.6546   $761.67   $761.65   $761.60