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 $36.74   11.644%   $41.018   $41.02   $41.00   $41.00  
  Purchase #2 $76.60   12.759%   $86.3734   $86.37   $86.35   $86.40  
  Purchase #3 $246.48   5.685%   $260.4924   $260.49   $260.50   $260.50  
  Purchase #4 $173.25   5.218%   $182.2902   $182.29   $182.30   $182.30  
  Purchase #5 $33.33   6.838%   $35.6091   $35.61   $35.60   $35.60  
  Purchase #6 $221.76   4.500%   $231.7392   $231.74   $231.75   $231.70  
  Purchase #7 $222.40   7.398%   $238.8532   $238.85   $238.85   $238.90  
  7 purchase totals = $1,010.56       $1,076.3755   $1,076.37   $1,076.35   $1,076.40