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 $105.94   8.161%   $114.5858   $114.59   $114.60   $114.60  
  Purchase #2 $205.93   12.233%   $231.1214   $231.12   $231.10   $231.10  
  Purchase #3 $57.94   5.683%   $61.2327   $61.23   $61.25   $61.20  
  Purchase #4 $195.39   10.106%   $215.1361   $215.14   $215.15   $215.10  
  Purchase #5 $118.71   6.238%   $126.1151   $126.12   $126.10   $126.10  
  Purchase #6 $178.54   13.230%   $202.1608   $202.16   $202.15   $202.20  
  Purchase #7 $104.75   11.138%   $116.4171   $116.42   $116.40   $116.40  
  7 purchase totals = $967.20       $1,066.7690   $1,066.78   $1,066.75   $1,066.70