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 $58.62   6.719%   $62.5587   $62.56   $62.55   $62.60  
  Purchase #2 $215.56   11.204%   $239.7113   $239.71   $239.70   $239.70  
  Purchase #3 $120.75   6.833%   $129.0008   $129.00   $129.00   $129.00  
  Purchase #4 $194.67   7.262%   $208.8069   $208.81   $208.80   $208.80  
  Purchase #5 $112.85   13.373%   $127.9414   $127.94   $127.95   $127.90  
  Purchase #6 $116.67   3.851%   $121.163   $121.16   $121.15   $121.20  
  Purchase #7 $248.35   4.184%   $258.741   $258.74   $258.75   $258.70  
  7 purchase totals = $1,067.47       $1,147.9231   $1,147.92   $1,147.90   $1,147.90