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 $218.95   8.452%   $237.4557   $237.46   $237.45   $237.50  
  Purchase #2 $196.75   3.393%   $203.4257   $203.43   $203.45   $203.40  
  Purchase #3 $98.54   7.131%   $105.5669   $105.57   $105.55   $105.60  
  Purchase #4 $225.88   9.241%   $246.7536   $246.75   $246.75   $246.80  
  Purchase #5 $122.89   8.599%   $133.4573   $133.46   $133.45   $133.50  
  Purchase #6 $167.36   12.719%   $188.6465   $188.65   $188.65   $188.60  
  Purchase #7 $35.58   10.117%   $39.1796   $39.18   $39.20   $39.20  
  7 purchase totals = $1,065.95       $1,154.4853   $1,154.50   $1,154.50   $1,154.60