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 $40.68   8.106%   $43.9775   $43.98   $44.00   $44.00  
  Purchase #2 $224.73   10.161%   $247.5648   $247.56   $247.55   $247.60  
  Purchase #3 $22.56   8.316%   $24.4361   $24.44   $24.45   $24.40  
  Purchase #4 $67.83   4.269%   $70.7257   $70.73   $70.75   $70.70  
  Purchase #5 $248.83   3.824%   $258.3453   $258.35   $258.35   $258.30  
  Purchase #6 $250.27   12.599%   $281.8015   $281.80   $281.80   $281.80  
  Purchase #7 $159.88   11.388%   $178.0871   $178.09   $178.10   $178.10  
  7 purchase totals = $1,014.78       $1,104.9380   $1,104.95   $1,105.00   $1,104.90