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 $119.54   5.323%   $125.9031   $125.90   $125.90   $125.90  
  Purchase #2 $28.81   11.620%   $32.1577   $32.16   $32.15   $32.20  
  Purchase #3 $79.51   6.421%   $84.6153   $84.62   $84.60   $84.60  
  Purchase #4 $216.44   4.645%   $226.4936   $226.49   $226.50   $226.50  
  Purchase #5 $181.94   3.484%   $188.2788   $188.28   $188.30   $188.30  
  Purchase #6 $224.76   12.686%   $253.2731   $253.27   $253.25   $253.30  
  Purchase #7 $125.55   6.723%   $133.9907   $133.99   $134.00   $134.00  
  7 purchase totals = $976.55       $1,044.7123   $1,044.71   $1,044.70   $1,044.80