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 $91.85   6.189%   $97.5346   $97.53   $97.55   $97.50  
  Purchase #2 $58.62   13.824%   $66.7236   $66.72   $66.70   $66.70  
  Purchase #3 $212.95   6.492%   $226.7747   $226.77   $226.75   $226.80  
  Purchase #4 $127.88   4.145%   $133.1806   $133.18   $133.20   $133.20  
  Purchase #5 $220.35   4.284%   $229.7898   $229.79   $229.80   $229.80  
  Purchase #6 $248.30   7.724%   $267.4787   $267.48   $267.50   $267.50  
  Purchase #7 $51.48   6.205%   $54.6743   $54.67   $54.65   $54.70  
  7 purchase totals = $1,011.43       $1,076.1563   $1,076.14   $1,076.15   $1,076.20