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 $68.45   11.325%   $76.202   $76.20   $76.20   $76.20  
  Purchase #2 $35.68   11.796%   $39.8888   $39.89   $39.90   $39.90  
  Purchase #3 $84.57   13.624%   $96.0918   $96.09   $96.10   $96.10  
  Purchase #4 $245.27   8.562%   $266.27   $266.27   $266.25   $266.30  
  Purchase #5 $203.75   13.626%   $231.513   $231.51   $231.50   $231.50  
  Purchase #6 $214.97   13.533%   $244.0619   $244.06   $244.05   $244.10  
  Purchase #7 $62.71   13.167%   $70.967   $70.97   $70.95   $71.00  
  7 purchase totals = $915.40       $1,024.9945   $1,024.99   $1,024.95   $1,025.10