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 $69.56   10.439%   $76.8214   $76.82   $76.80   $76.80  
  Purchase #2 $200.90   8.788%   $218.5551   $218.56   $218.55   $218.60  
  Purchase #3 $162.70   13.234%   $184.2317   $184.23   $184.25   $184.20  
  Purchase #4 $239.56   3.646%   $248.2944   $248.29   $248.30   $248.30  
  Purchase #5 $56.28   7.484%   $60.492   $60.49   $60.50   $60.50  
  Purchase #6 $48.53   5.870%   $51.3787   $51.38   $51.40   $51.40  
  Purchase #7 $197.42   13.173%   $223.4261   $223.43   $223.45   $223.40  
  7 purchase totals = $974.95       $1,063.1994   $1,063.20   $1,063.25   $1,063.20