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 $86.88   9.312%   $94.9703   $94.97   $94.95   $95.00  
  Purchase #2 $240.99   13.321%   $273.0923   $273.09   $273.10   $273.10  
  Purchase #3 $72.25   7.524%   $77.6861   $77.69   $77.70   $77.70  
  Purchase #4 $102.98   5.356%   $108.4956   $108.50   $108.50   $108.50  
  Purchase #5 $48.50   9.655%   $53.1827   $53.18   $53.20   $53.20  
  Purchase #6 $246.84   3.230%   $254.8129   $254.81   $254.80   $254.80  
  Purchase #7 $97.72   8.783%   $106.3027   $106.30   $106.30   $106.30  
  7 purchase totals = $896.16       $968.5426   $968.54   $968.55   $968.60