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 $58.46   5.483%   $61.6654   $61.67   $61.65   $61.70  
  Purchase #2 $245.68   5.658%   $259.5806   $259.58   $259.60   $259.60  
  Purchase #3 $12.97   10.416%   $14.321   $14.32   $14.30   $14.30  
  Purchase #4 $24.32   12.522%   $27.3654   $27.37   $27.35   $27.40  
  Purchase #5 $123.96   11.686%   $138.446   $138.45   $138.45   $138.40  
  Purchase #6 $215.29   5.192%   $226.4679   $226.47   $226.45   $226.50  
  Purchase #7 $8.36   4.489%   $8.7353   $8.74   $8.75   $8.70  
  7 purchase totals = $689.04       $736.5816   $736.60   $736.55   $736.60