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 $69.95   5.280%   $73.6434   $73.64   $73.65   $73.60  
  Purchase #2 $196.43   10.326%   $216.7134   $216.71   $216.70   $216.70  
  Purchase #3 $207.56   7.236%   $222.579   $222.58   $222.60   $222.60  
  Purchase #4 $71.56   13.677%   $81.3473   $81.35   $81.35   $81.30  
  Purchase #5 $170.63   13.846%   $194.2554   $194.26   $194.25   $194.30  
  Purchase #6 $243.99   5.761%   $258.0463   $258.05   $258.05   $258.00  
  Purchase #7 $167.70   13.661%   $190.6095   $190.61   $190.60   $190.60  
  7 purchase totals = $1,127.82       $1,237.1943   $1,237.20   $1,237.20   $1,237.10