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 $88.36   7.798%   $95.2503   $95.25   $95.25   $95.30  
  Purchase #2 $87.64   10.230%   $96.6056   $96.61   $96.60   $96.60  
  Purchase #3 $50.95   11.589%   $56.8546   $56.85   $56.85   $56.90  
  Purchase #4 $168.93   12.207%   $189.5513   $189.55   $189.55   $189.60  
  Purchase #5 $234.81   3.719%   $243.5426   $243.54   $243.55   $243.50  
  Purchase #6 $220.53   10.795%   $244.3362   $244.34   $244.35   $244.30  
  Purchase #7 $9.60   8.697%   $10.4349   $10.43   $10.45   $10.40  
  7 purchase totals = $860.82       $936.5755   $936.57   $936.60   $936.60