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 $61.67   11.305%   $68.6418   $68.64   $68.65   $68.60  
  Purchase #2 $164.46   10.796%   $182.2151   $182.22   $182.20   $182.20  
  Purchase #3 $72.59   12.748%   $81.8438   $81.84   $81.85   $81.80  
  Purchase #4 $13.90   12.581%   $15.6488   $15.65   $15.65   $15.60  
  Purchase #5 $219.93   6.742%   $234.7577   $234.76   $234.75   $234.80  
  Purchase #6 $148.68   3.360%   $153.6756   $153.68   $153.70   $153.70  
  Purchase #7 $115.73   8.255%   $125.2835   $125.28   $125.30   $125.30  
  7 purchase totals = $796.96       $862.0663   $862.07   $862.10   $862.00