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 $59.66   4.683%   $62.4539   $62.45   $62.45   $62.50  
  Purchase #2 $106.81   13.616%   $121.3532   $121.35   $121.35   $121.40  
  Purchase #3 $115.76   13.167%   $131.0021   $131.00   $131.00   $131.00  
  Purchase #4 $51.80   4.645%   $54.2061   $54.21   $54.20   $54.20  
  Purchase #5 $178.93   6.813%   $191.1205   $191.12   $191.10   $191.10  
  Purchase #6 $141.25   6.409%   $150.3027   $150.30   $150.30   $150.30  
  Purchase #7 $6.42   4.252%   $6.693   $6.69   $6.70   $6.70  
  7 purchase totals = $660.63       $717.1315   $717.12   $717.10   $717.20