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 $62.76   4.545%   $65.6124   $65.61   $65.60   $65.60  
  Purchase #2 $75.66   13.786%   $86.0905   $86.09   $86.10   $86.10  
  Purchase #3 $163.71   11.377%   $182.3353   $182.34   $182.35   $182.30  
  Purchase #4 $17.58   6.604%   $18.741   $18.74   $18.75   $18.70  
  Purchase #5 $81.97   6.108%   $86.9767   $86.98   $87.00   $87.00  
  Purchase #6 $229.35   10.143%   $252.613   $252.61   $252.60   $252.60  
  Purchase #7 $193.80   4.781%   $203.0656   $203.07   $203.05   $203.10  
  7 purchase totals = $824.83       $895.4345   $895.44   $895.45   $895.40