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 $76.48   7.359%   $82.1082   $82.11   $82.10   $82.10  
  Purchase #2 $152.54   7.245%   $163.5915   $163.59   $163.60   $163.60  
  Purchase #3 $217.29   5.296%   $228.7977   $228.80   $228.80   $228.80  
  Purchase #4 $12.61   13.704%   $14.3381   $14.34   $14.35   $14.30  
  Purchase #5 $180.92   11.853%   $202.3644   $202.36   $202.35   $202.40  
  Purchase #6 $118.46   4.284%   $123.5348   $123.53   $123.55   $123.50  
  Purchase #7 $10.56   8.638%   $11.4722   $11.47   $11.45   $11.50  
  7 purchase totals = $768.86       $826.2069   $826.20   $826.20   $826.20