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 $208.37   8.456%   $225.9898   $225.99   $226.00   $226.00  
  Purchase #2 $211.84   5.270%   $223.004   $223.00   $223.00   $223.00  
  Purchase #3 $97.26   8.448%   $105.4765   $105.48   $105.50   $105.50  
  Purchase #4 $33.59   5.354%   $35.3884   $35.39   $35.40   $35.40  
  Purchase #5 $195.60   5.793%   $206.9311   $206.93   $206.95   $206.90  
  Purchase #6 $246.26   8.791%   $267.9087   $267.91   $267.90   $267.90  
  Purchase #7 $184.77   7.126%   $197.9367   $197.94   $197.95   $197.90  
  7 purchase totals = $1,177.69       $1,262.6352   $1,262.64   $1,262.70   $1,262.60