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 $22.83   5.335%   $24.048   $24.05   $24.05   $24.00  
  Purchase #2 $107.29   7.281%   $115.1018   $115.10   $115.10   $115.10  
  Purchase #3 $201.74   8.372%   $218.6297   $218.63   $218.65   $218.60  
  Purchase #4 $111.38   7.556%   $119.7959   $119.80   $119.80   $119.80  
  Purchase #5 $164.97   8.141%   $178.4002   $178.40   $178.40   $178.40  
  Purchase #6 $138.94   11.254%   $154.5763   $154.58   $154.60   $154.60  
  Purchase #7 $240.27   5.124%   $252.5814   $252.58   $252.60   $252.60  
  7 purchase totals = $987.42       $1,063.1333   $1,063.14   $1,063.20   $1,063.10