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 $59.65   3.442%   $61.7032   $61.70   $61.70   $61.70  
  Purchase #2 $80.48   4.271%   $83.9173   $83.92   $83.90   $83.90  
  Purchase #3 $111.32   5.701%   $117.6664   $117.67   $117.65   $117.70  
  Purchase #4 $126.77   12.339%   $142.4122   $142.41   $142.40   $142.40  
  Purchase #5 $219.70   10.634%   $243.0629   $243.06   $243.05   $243.10  
  Purchase #6 $126.34   6.605%   $134.6848   $134.68   $134.70   $134.70  
  Purchase #7 $219.90   5.280%   $231.5107   $231.51   $231.50   $231.50  
  7 purchase totals = $944.16       $1,014.9575   $1,014.95   $1,014.90   $1,015.00