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 $164.34   13.768%   $186.9663   $186.97   $186.95   $187.00  
  Purchase #2 $197.74   7.424%   $212.4202   $212.42   $212.40   $212.40  
  Purchase #3 $44.25   10.283%   $48.8002   $48.80   $48.80   $48.80  
  Purchase #4 $59.69   4.141%   $62.1618   $62.16   $62.15   $62.20  
  Purchase #5 $80.54   6.255%   $85.5778   $85.58   $85.60   $85.60  
  Purchase #6 $248.76   5.637%   $262.7826   $262.78   $262.80   $262.80  
  Purchase #7 $70.94   4.531%   $74.1543   $74.15   $74.15   $74.20  
  7 purchase totals = $866.26       $932.8632   $932.86   $932.85   $933.00