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 $182.49   7.413%   $196.018   $196.02   $196.00   $196.00  
  Purchase #2 $229.50   8.561%   $249.1475   $249.15   $249.15   $249.10  
  Purchase #3 $22.27   11.493%   $24.8295   $24.83   $24.85   $24.80  
  Purchase #4 $239.54   3.573%   $248.0988   $248.10   $248.10   $248.10  
  Purchase #5 $185.25   9.647%   $203.1211   $203.12   $203.10   $203.10  
  Purchase #6 $233.56   10.670%   $258.4809   $258.48   $258.50   $258.50  
  Purchase #7 $203.95   6.376%   $216.9539   $216.95   $216.95   $217.00  
  7 purchase totals = $1,296.56       $1,396.6497   $1,396.65   $1,396.65   $1,396.60