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 $118.39   6.631%   $126.2404   $126.24   $126.25   $126.20  
  Purchase #2 $249.88   10.324%   $275.6776   $275.68   $275.70   $275.70  
  Purchase #3 $107.44   7.849%   $115.873   $115.87   $115.85   $115.90  
  Purchase #4 $114.87   5.869%   $121.6117   $121.61   $121.60   $121.60  
  Purchase #5 $87.79   7.269%   $94.1715   $94.17   $94.15   $94.20  
  Purchase #6 $128.73   8.253%   $139.3541   $139.35   $139.35   $139.40  
  Purchase #7 $219.58   5.536%   $231.7359   $231.74   $231.75   $231.70  
  7 purchase totals = $1,026.68       $1,104.6642   $1,104.66   $1,104.65   $1,104.70