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 $33.72   6.568%   $35.9347   $35.93   $35.95   $35.90  
  Purchase #2 $214.54   11.393%   $238.9825   $238.98   $239.00   $239.00  
  Purchase #3 $246.92   6.250%   $262.3525   $262.35   $262.35   $262.40  
  Purchase #4 $122.74   3.760%   $127.355   $127.36   $127.35   $127.40  
  Purchase #5 $125.74   9.710%   $137.9494   $137.95   $137.95   $137.90  
  Purchase #6 $72.28   5.679%   $76.3848   $76.38   $76.40   $76.40  
  Purchase #7 $192.72   12.704%   $217.2031   $217.20   $217.20   $217.20  
  7 purchase totals = $1,008.66       $1,096.1620   $1,096.15   $1,096.20   $1,096.20