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 $43.92   5.515%   $46.3422   $46.34   $46.35   $46.30  
  Purchase #2 $224.37   10.699%   $248.3753   $248.38   $248.40   $248.40  
  Purchase #3 $197.30   4.253%   $205.6912   $205.69   $205.70   $205.70  
  Purchase #4 $32.63   3.177%   $33.6667   $33.67   $33.65   $33.70  
  Purchase #5 $198.67   9.783%   $218.1059   $218.11   $218.10   $218.10  
  Purchase #6 $62.29   3.242%   $64.3094   $64.31   $64.30   $64.30  
  Purchase #7 $247.28   4.238%   $257.7597   $257.76   $257.75   $257.80  
  7 purchase totals = $1,006.46       $1,074.2504   $1,074.26   $1,074.25   $1,074.30