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 $114.95   9.260%   $125.5944   $125.59   $125.60   $125.60  
  Purchase #2 $74.35   13.816%   $84.6222   $84.62   $84.60   $84.60  
  Purchase #3 $72.71   9.358%   $79.5142   $79.51   $79.50   $79.50  
  Purchase #4 $163.91   4.701%   $171.6154   $171.62   $171.60   $171.60  
  Purchase #5 $40.43   11.505%   $45.0815   $45.08   $45.10   $45.10  
  Purchase #6 $206.90   8.816%   $225.1403   $225.14   $225.15   $225.10  
  Purchase #7 $177.68   4.727%   $186.0789   $186.08   $186.10   $186.10  
  7 purchase totals = $850.93       $917.6469   $917.64   $917.65   $917.60