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 $43.58   5.595%   $46.0183   $46.02   $46.00   $46.00  
  Purchase #2 $247.54   7.670%   $266.5263   $266.53   $266.55   $266.50  
  Purchase #3 $103.44   11.203%   $115.0284   $115.03   $115.05   $115.00  
  Purchase #4 $114.87   12.235%   $128.9243   $128.92   $128.90   $128.90  
  Purchase #5 $169.42   9.620%   $185.7182   $185.72   $185.70   $185.70  
  Purchase #6 $245.95   7.759%   $265.0333   $265.03   $265.05   $265.00  
  Purchase #7 $95.69   9.487%   $104.7681   $104.77   $104.75   $104.80  
  7 purchase totals = $1,020.49       $1,112.0169   $1,112.02   $1,112.00   $1,111.90