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 $42.76   8.178%   $46.2569   $46.26   $46.25   $46.30  
  Purchase #2 $206.91   12.678%   $233.142   $233.14   $233.15   $233.10  
  Purchase #3 $104.64   13.318%   $118.576   $118.58   $118.60   $118.60  
  Purchase #4 $84.75   11.583%   $94.5666   $94.57   $94.55   $94.60  
  Purchase #5 $248.67   7.176%   $266.5146   $266.51   $266.50   $266.50  
  Purchase #6 $161.58   8.173%   $174.7859   $174.79   $174.80   $174.80  
  Purchase #7 $156.40   7.279%   $167.7844   $167.78   $167.80   $167.80  
  7 purchase totals = $1,005.71       $1,101.6264   $1,101.63   $1,101.65   $1,101.70