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 $204.79   4.592%   $214.194   $214.19   $214.20   $214.20  
  Purchase #2 $182.89   3.662%   $189.5874   $189.59   $189.60   $189.60  
  Purchase #3 $167.53   12.358%   $188.2334   $188.23   $188.25   $188.20  
  Purchase #4 $204.95   12.112%   $229.7735   $229.77   $229.75   $229.80  
  Purchase #5 $128.72   11.597%   $143.6477   $143.65   $143.65   $143.60  
  Purchase #6 $103.44   10.320%   $114.115   $114.12   $114.10   $114.10  
  Purchase #7 $53.89   4.296%   $56.2051   $56.21   $56.20   $56.20  
  7 purchase totals = $1,046.21       $1,135.7561   $1,135.76   $1,135.75   $1,135.70