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 $60.58   4.659%   $63.4024   $63.40   $63.40   $63.40  
  Purchase #2 $175.99   3.783%   $182.6477   $182.65   $182.65   $182.60  
  Purchase #3 $89.83   3.730%   $93.1807   $93.18   $93.20   $93.20  
  Purchase #4 $106.70   9.630%   $116.9752   $116.98   $117.00   $117.00  
  Purchase #5 $152.78   13.198%   $172.9439   $172.94   $172.95   $172.90  
  Purchase #6 $226.41   11.526%   $252.506   $252.51   $252.50   $252.50  
  Purchase #7 $197.26   4.478%   $206.0933   $206.09   $206.10   $206.10  
  7 purchase totals = $1,009.55       $1,087.7492   $1,087.75   $1,087.80   $1,087.70